I personally think doomsday might just pull this off. The way I see it, superman had to give literally everything he physically, mentally, and emotionally had to stop doomsday, which ended up killing both of them. Normally, an important distinction I would make between superman and Zod would be that superman wouldn’t go that extra distance, or kill, to stop an enemy while zod would, meaning sometimes superman May hold back while zod wouldn’t. This changed During the doomsday fight and doomsday still almost won, which could even be argued doomsday did win. The one argument I could say for zod would be that zod has actual training to fight, potentially making him a little bit deadlier of a combatant. However, I still think I’d put my money on doomsday. Those are just my two cents though, and I could probably see why people would argue that zod could/would win.