Zack Snyder’s Justice League showcases an epic battle between the Greek Gods and young Darkseid during his first invasion of Earth many years ago. However, while the gods were able to repel the Apokoliptan forces in the movie, Darkseid also had a feud with the Olympians in the comics - and the outcome was very different.
While the Olympians are referred to as the "Old Gods” in Zack Snyder’s Justice League, it's important to note that they are actually entirely different groups in the comics. In DC lore, the Old Gods predated the Olympians and were loosely based on Norse mythology. Though they were immensely powerful, the Old Gods eventually met their end during an event called Ragnarok, and their destruction gave way to the rise of several new pantheons, including the Olympians and the New Gods of Apokolips and New Genesis. In Wonder Woman #19 by George Pérez, Circe explains to Diana that after the Olympians seized power on Earth by defeating the Titans, they used magic to hide their existence from Darkseid and other dangerous cosmic beings, so as to prevent an invasion while they recovered from the war. The magic held up for a time, but eventually, Darkseid discovered the Olympians and devised a plan to usurp them.
Rather than lead with a full-scale invasion like in the movie, Darkseid - who still went by his original name Uxas at the time - instead took a more subtle approach. Wonder Woman #132 by John Byrne explains how the Olympians’ power stems from “the worship and devotion of mortals.” The Olympians primarily held power in Greece, so Uxas disguised himself as a wandering preacher and secretly spread tales of the Greek Gods in Rome. Athena tells Diana that Uxas had “intuited what we had only begun to learn…mortals control the gods every bit as much as we control them!” With a growing number of followers in Rome, the gods decided to establish another Olympus in the mountains of Italy and used their power to create avatars of themselves, allowing them to literally be in two places at once. In doing so, the Olympians unknowingly decreased their overall might. The separated avatars slowly began to develop personalities of their own, and eventually became entirely different entities. “We divided ourselves,” Athena says, “and thus fell victims to the plan of Uxas…he knew that if we were split into two pantheons, each would be less powerful than the whole!"
With the Olympians’ power spent, Uxas focussed his efforts elsewhere, eventually becoming the Lord of Apokolips called Darkseid. With an army at his back, the time finally came for Darkseid to ready his armada and attack Olympus. In Action Comics #600 by John Byrne and George Pérez, Wonder Woman and Superman are called to Olympus during Darkseid’s invasion. However, after fighting their way to Darkseid himself, Wonder Woman reveals that the villain’s conquest is too late- the Greek Gods had already relocated across the cosmos, far from Darkseid’s reach. Enraged, Darkseid attempted to destroy the abandoned Olympus, but even the mountain refused to crumble. “Olympus is eternal,” Wonder Woman explains, “not even Darkseid can destroy it. It will pass only when the gods themselves wish it to be so.” And so Darkseid retreated back to Apokolips empty handed, robbed of his glory.
Darkseid may have missed his chance to properly conquer the Olympians, but it was his meddling that ultimately led to their exodus from Earth, which is more of a win than he got in the movie. Still, Darkseid wouldn’t be DC’s biggest villain if he was satisfied with a draw, so Zeus and the Olympians had better keep watching their backs.