Post Apocalyptic Mayhem

Ok, since there are so many post apocalypse scenarios (aliens, nukes, robots, disease, zombies, etc.) How many are too many? I am almost afraid that I'm combining too many right now with the zombies and the post apocalypse but I still feel they go hand in hand. Only problem is I want to add some other elements too, but doing so might make it excessive and limit the story that exists. So today's (short) post is to ask people what they think. Is it bad to combine 3 of these? I think it could be done but I want to know what you readers think. Leave me a comment!