@welcome2atlantis I forget its name right now, but I had found a webcomic once that was roughly about that sort of thing. If a zombie in that setting ate enough human brains, it could regain human intelligence itself. Continued consumption to maintain that was required. The story takes place after quite an amount of zombies have basically rebuilt society for themselves, so either humans were basically cattle or they were using cloned brains to survive or something.
Naturally, the main character is a human, so he's playing on hard mode.