we have to guess that Zod would have betrayed us, and him. but considering Lois was still alive when Superman was unconscious, we don't really have any reason to believe he was lying, or she would have been killed immediately. Its entirely possible if Clark said ok, ill go with you. They would have taken him and went to another planet to terraform. (granted if they did have a scene that made it clear, Zod was lying, then that would probably be entirely too cliche. but really as it stands, clark is made out to be a giant asshole.)
Your movie has a serious problem if the hero can solve everything, by doing nothing.