Wait, we're still going over all this? I thought it was as obvious as can be that Zod wanted Superman to kill him at that point. That's what all the stuff about him no longer having any purpose anymore was all about.
Instead of continuing to fight on and on, he decided to force Superman's hand and give him no choice but to kill him.
Yeah, we're still going over it. I'm willing to admit I don't fucking remember every moment from a movie I didn't like and haven't watched since walking out of the theater.
Edited to add: Sorry, just frustrated.