system
Given the following post, respond as if you're commenting on Reddit:
human
[Man of Steel] Why did Zod want to terraform Earth?

Earth's natural environment is clearly better for Kryptonians, giving them god like powers. The movie also makes it clear that with enough concentration, they'd be able to overcome the side effects of its atmosphere in a couple of days at most. What was the point of committing mass genocide? They probably would have been successful in taking over Earth if they hadn't tried to terraform. There's no way Superman could have stopped all of them on his own if it came down to a pure fight.
gpt
Zod wants to recreate Krypton exactly as it was - minus a few 'troublesome' bloodlines that ended up endangering it to begin with - or as close as he can manage. A world where everyone are basically physical gods that can punch through mountains, fly into space at supersonic speeds, shoot lasers from their eyes, etc. is not going to be the Krypton he wants and, as a society, may very well be inherently self-destructive. To do anything less than his utmost to bring back Krypton as close to its original state as he can manage is anathema to Zod. It's literally part of his DNA.

On top of that, Zod and Faora were able to adjust so quickly because they were bred soldiers, trained over their entire lifetimes to have total control of themselves. The average Kryptonian is probably going to have a much tougher time. Clark is mentioned as having severe breathing difficulties as a baby. It's not unreasonable to assume that it's a very real possibility that he, and by extension other Kryptonian children, could have died in Earth's atmosphere.