Egyptian to Greek mythology
A general visual of how, Egyptian mythology, namely: Heliopolis creation myth (2800BC) turned Hermopolis creation myth (2400) turned Theban creation myth (2050BC), became Greek mythology (800BC), wherein Shu, the Egyptian god who separates Geb (earth) from Nut (heaven), becomes the Greek Atlas, who holds up the heavens, Amen-Ra became Zeus, Osiris became Dionysus, and Set became Typhon, to name a few (see: god character equivalences).
In mythology, Greek mythology, generally based on Hermopolis creation myth, via Homer (800BC), where the Ogdoad became the primordial deities, Atum-Ra (or Amen-Ra) became Zeus, and the Ennead became the Gaia (earth) and Uranus (sky) who procreate the warring factions of the Olympians and the Titans, generally modeled on the great war between Osiris and his faction and Set and his faction.

In Greece, during their rise to power (see: histomap), scholars, such as Homer (c.800BC), Hesiod (c.800BC), and Virgil (30BC), learned of the god structure of the Egyptians, in large part, and rewrote their own god genealogy in modified template form, based on the Egyptian models of the Heliopolis creation myth, Memphis creation myth, Hermopolis creation myth, Theban creation myth, Ennead, and Ogdoad; Plutarch put things as follows:

“They say that the sun and moon do not use chariots, but boats in which to sail round in their courses; and by this they intimate that the nourishment and origin of these heavenly bodies is from moisture. They think also that Homer, like Thales, had gained his knowledge from the Egyptians, when he postulated water as the source and origin of all things; for, according to them, Oceanus is Osiris, and Tethys is Isis, since she is the kindly nurse and provider for all things. In fact, the Greeks call emission apousia and coition synousia, and the son (hyios) from water (hydor) and rain (hysai); Dionysus also they call Hyes since he is lord of the nature of moisture; and he is no other than Osiris. In fact, Hellanicus seems to have heard Osiris pronounced ‘Hysiris’ by the priests, for he regularly spells the name in this way, deriving it, in all probability, from the nature of Osiris and the ceremony of finding him.”
Plutarch (100AD), On Isis and Osiris (§34)

The Egyptian god Shu, e.g., in slightly re-written fashion, became the Greek god Atlas who with his brother Menoetius sided with the Titans in their war against the Olympians, the Titanomachy. When the Titans were defeated, many of them (including Menoetius) were confined to Tartarus, but Zeus condemned Atlas to stand at the western edge of Gaia (the Earth), according to the Virgil (30BC) version, and hold up the “sky” (or Nut, in original Egyptian version) on his shoulders, to prevent the two from resuming their primordial embrace. (Ѻ)

In c.680BC, Orpheus (c.725-675BC), according to Diodorus (c.40BC), travelled from Thrace to Egypt, wherein he was initiated into the mysteries of an Egyptian “Dionysus”, aka Osiris, which he brought back to Greece; Aaron Johnson summarizes (Ѻ) this line of argument as follows:

“When Orpheus visited Egypt in search of wisdom and knowledge, he was initiated into the mysteries of Osiris/Dionysus, but wanting to make the Thebans of Greece happy, he changed the place of Dionysus’ birth to Hellenic Thebes and then initiate the Thebans in the mysteries.”

In c.580BC, Greek reformer Solon (c.638-558BC), according to Plato (Ѻ), substituted Greek names for Egyptian ones, in writing about the deities, according to which Amen-Ra became Zeus, Set became Typhon, Osiris became Dionysus, Horus became Hercules, Shu became Atlas, etc. Solon, according to Plutarch, spent some time in Egypt and discussed philosophy with two Egyptian priests, Psenophis of Heliopolis and Sonchis of Sais. Solon, according to Plato's dialogues Timaeus and Critias, visited Neith's temple at Sais (see: recension theory) and received from the priests there an account of the history of Atlantis. (Ѻ)

In 435BC, Greek historian Herodotus, in his Histories (pgs. 92; 100), based on first-hand interviews, attempted to summarize the convolution of Egyptian and Greek gods as follows (truncate quote):

“Ethiopians inhabit the country immediately above Elephantine, and one half of the island; the other half is inhabited by Egyptians. Meroe is said to be the capital of all Ethiopia. The inhabitants worship no other gods than Jupiter and Bacchus; but these they honor with great magnificence; they have also an oracle of Jupiter; and they make war, whenever that god bids them by an oracular warning, and against whatever country he bids them. All those who have a temple erected to Theban Jupiter, or belong to the Theban district, abstain from sheep, and sacrifice goats only. For the Egyptians do not all worship the same gods in the same manner, except Isis and Osiris, who, they say, is Bacchus; but these deities they all worship in the same manner.”

In 40BC, Greek historian Diodorus Siculus, in his 20-volume Historical Library, stated the following (aggregate quote):

“The initiatory rites of Demeter in Eleusis were transferred from Egypt (1.29.2). The rite of Osiris is the same as that of Dionysus and that of Isis very similar to that of Demeter; the names alone having been interchanged, and the punishments in Hades of the unrighteous, the Fields of the Righteous and the fantastic conceptions, current among the many - all these were introduced by Orpheus in imitation of the Egyptian funeral customs. (1.96.4-5). Isis, after having invented the practice of medicine, taught this art to her son Orus [Horus], named also Apollo, who was the last of the gods that reigned in Egypt.”

In c.50AD, Cornutus commented on the comment on the Osiris and Dionysus/Bacchus equivalence.

In 100AD, Greek-born Roman historian Plutarch, in his On Isis and Osiris, stated the following:

“The histories on which the most solemn feasts of Bacchus, the Titania and Nuktelia, are founded, exactly correspond with what are related of the cutting to pieces of Osiris, of his rising again, and of his new life.”

This point is generally considered the start of the need to make Egyptian to Greek to Roman god equivalency tables, per reason that one needs these translation equivalents so to be able to read Plutarch's account of things cogently.

Titans | Olympians
In 700BC, Hermopolis creation myth, with its two primordial god families, i.e. Ogdoad and Ennead, became, via the Greek scholars travelling to Egypt to study under their priests, Hesiod, as detailed in his Theogony (c.700BC), and Homer, in particular, became rewritten such that the Ogdoad became the Greek “primordial deities” (Ѻ) and the Ennead, in a general sense, becomes the god family (Ѻ) of the “Titans” and the “Olympians”, the where the war that famously ensues is the rescript of the famous battle between Set and Horus and on the question of the right to rule over both Upper and Lower Egypt.

The following are related quotes:

“The trumpets they conceal in Bacchic wands (see: Thyrsus), as Socrates has stated in his treatise on The Holy Ones. Furthermore, the tales regarding the Titans and the rites celebrated by night agree with the accounts of the dismemberment of Osiris and his revivification and regenesis.”
Plutarch (100AD), On Isis and Osiris (§35)

“A tradition says Solon (638-558), Thales, and Plato all visited the great college at Heliopolis, and that the last-named actually studied there, and that Manetho (c.300-250BC), the priest of Sebennytus, who wrote a history of Egypt in Greek for Ptolemy II., collected his materials in the library of the priesthood of Ra.”
Wallis Budge (1904), The Gods of the Egyptians [1]

“Interesting to note the parallels to certain Greek myths. Ra foresees that the children of Nut will overtake him, and taking steps to prevent them from doing so, just as Uranus and Cronus foresaw and attempted to prevent their own overthrow by their own children. Even more strikingly, Isis goes on a search for her lost husband, goes to work for a noble family in disguise, and attempts to make their child immortal by burning their mortal flesh away, before being interrupted by the child's mother, and growing wrathful. This is markedly similar to one version of the myth of Demeter and Persephone, in which Demeter, after searching for her lost daughter for several days, comes across a town, where she takes up a disguise, goes to work for a noble family, grows fond of their child, and tries to make the child immortal by burning away his mortal flesh, before being interrupted by the mother, and placing a curse on the town in vengeance. I wonder... did the Greeks borrow this myth from the Egyptian, do both stem from some older myth, or are the similarities somehow just coincidental?”
— Erudito otidurE (2018), thread comment on Osiris Myth Animated [2]

1. Budge, Wallis. (1904). The Gods of the Egyptians, Volume One (pg. 332). Dover, 1969.
2. Anon. (2018). “Egyptian Mythology: Osiris Myth Animated” (Ѻ), Captivating History, YouTube, Jun 14.

External links
Greek mythology – Wikipedia.

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