In terms of improvement, there are many things that have visibly amped up in Zack Snyder's Justice League. Whether you count the better visual effects, an infinitely improved Batman and Wonder Woman, or the fact that Snyder rectified many of the plot holes created by the theatrical version of the film. But despite his immaculate treatment of the story, he still left behind a rather confusing plot hole-- Darkseid forgetting that the Anti-Life Equation existed on Earth despite it being the only planet that fought his invasion and won. But Snyder has an answer ready to explain away this inconsistency.
Apparently, Darkseid not remembering this crucial piece of information is explainable after all. Recently Zack Snyder was questioned by a fan about Darkseid forgetting the one planet that defeated him. He came to Earth with the Mother Boxes, found the Anti-Life Equation here, and yet he doesn't remember a thing. In fact, it's Steppenwolf who discovers the equation and informs his master, who is surprisingly shocked to hear the news. Why?
"He almost died when he returned to apocalypse he was in a fight for power and much time passed before he was in a position of power again and by then all who had been with him had been Slayed."
According to Snyder, there are multiple reasons why Darkseid forgot Earth as the planet housing the Anti-Life Equation. For starters, he was grievously injured from Ares' attack when he was whisked away from Earth by his minions. Adding to the blurry confusion of all the chaos that followed is a long struggle for power. From the dialogues in the Snyder Cut, it's obvious that Darkseid was not always in power- there was once a coup planned to take his throne and he fought back to regain power. Steppenwolf was one of the few who tried to betray Darkseid and failed. That's why he is on Earth- he is annexing planets for his master, repaying his debt to Darkseid for not killing him, and waiting to be allowed back home.
Thus, for a very long time, after returning from Earth in a severely injured state, Darkseid was busy in a fight for power and according to Zack Snyder it took him a long time to regain that lost power. In the ensuing battles, all those who had fought by his side on Earth had died. And that's why Darkseid had no recollection that the "world that fought back" was also the one where the Anti-Life Equation.
A bit flimsy, don't you think?
Darkseid is a conqueror of worlds- he defeated and dominated thousands of worlds to annex them completely. So, for such a habitual winner, losing to a tiny planet and in fact, coming back defeated is a memory that should have been seared in his mind. After all it was the mighty ruler of Apokolips defeated by a puny planet! And yet, being injured and fighting a power battle somehow mind-washed him?
What could have been a more plausible explanation was that when Darkseid invaded Earth eons ago, he was met with an army of Amazonians, Atlanteans, Humans, Gods, and other alien races. It could have made impossible for him to recognize that it was actually the "land of men," i.e., Earth.
What further contributed to his selective amnesia is that Earth has been constantly shifting and changing. After Darkseid's invasion, eons went by during which the planet's appearance and location in the universe might have changed, making it harder for Darkseid to recognize it from the millions of planets he still has to annex.
But apparently, this is not the reason. According to Zack Snyder, a life-threatening blow to his shoulder and thousands of years of power struggle were the ones that erased the memory of him invading Earth from his mind. Oh, well. The news comes to us via Vero.