Why not terraform Venus?

Well, to be fair to MoS they did establish it was the atmosphere that gives them powers, not sunlight like it should have been. Meaning they would die on Venus. But you actually are right. Clearly if they could turn a prison into an FTL ship then reengineer that ship to world engine a planet... surely they could have terraformed Venus or Mars (I'd go with mars personally, you'd have to put less crap in the atmosphere to get the average radiation and or temperature down.)

You are absolutely right, Zod was an idiot. He's leading an endangered species and WAR is his first choice? As advanced as they are is any amount of risk to the very few members of his entire species worth anything they could gain by conflict? To a rational mind... no.

"Who built this f#(%!^g police station." -- Leon Kennedy

Zod, despite all his speechifying about protecting Krypton, not only wanted to remake Krypton through what he saw as superior bloodlines, he wanted to exact vengeance on Kal-El--not just find the codex. He said it to Lara ("I will find him!") before being banished to the Phantom Zone,

Later, when he's arguing with Jor-El's computer program consciousness, Zod says: "You have Jor-El's memories; his conscience. Can you experience his pain? I will harvest the codex from your son's corpse, and I will rebuild Krypton atop his bones."

Zod wanted vengeance more than he wanted to rebuild Krypton. He wasn't some focused man of principle who only wanted to save Krypton as he was born to do. No, Zod wanted to do it at the expense of Jor-El--ghost or otherwise--and Kal-El's life.

So terraforming Venus or any other planet where the son of Jor-El does not reside just doesn't make sense to a twisted villain like Zod.

Hope that clears everything up.

Jor-El told World Engines were used to adapt atmospheric environments, not to create atmospheres, and even when Kal-El asks why Earth, Zod says "Foundations must be build on somerhing", as if it's necessary some kind of "valid sustract". Plus, we can suppose the world engine doesn't work on any environment, as the previous users perished even having one, and considering Zod's crew were almost out of power (they an't even switch on the world engine alone, but using the ship as a slave supplier) and hadn't used the machine yet.

All that elements and facts might tell that the world engine doesn't work magically everywhere, or if it would, most of its users were kind of unprofessional in obtaining results with it.

My conclusion: It's pretty evident the world engine has its limitations, and can adapt existing habitable environments to optim conditions for krytponians, but can't create habitable ambients from nothing.

They didn't know about the powers they would get when they first came to Earth.

They saw life on Earth, plants, etc just like Krypton and so it made the most sense.

Kal-El was the first natural birth on Krypton in centuries. Unlike most of them he wasn't engineered. The rest of his people were designed for specific functions, making their race like a complicated hive with many castes. Zod and his people were soldiers for example. But the death of Kryptonian civilization, on their homeworld and every single one of their colonies, showed that their system was fundamentally flawed. Something Zod could never see. His failure to find an alternative to exterminating humanity had more to do with not wanting to share power with them than any practical consideration - and his fanatical devotion to his mission drove him to irrational extremes. A tunnel vision he suffered because of his own nature which, again, he was blind to.

If the world engine could transform the Earth's environment it could probably have done the same on Venus, or Mars. Or Zod could have just founded a new society on one of the other planets where his people had already lived, once he had the codex. I'm sure Superman would have given it to him voluntarily if not for his plan to kill off the human race. You have to wonder about a giant terraforming machine that has automated defenses though. Why build those in, unless you're expecting attacks by desperate natives trying to shut it down? Were those General Zod's additions or were ancient Kryptonians in the business of terraforming worlds whether they were already inhabited or not?

Because Zod is on a mission and doesn't want to waste time. He doesn't consider the humans a threat, and neither Superman for that matter because his powers were nullified.

I guess they could have. For us it would be nearly impossible but for them? Hmmmmm.

I don't know.