My son is a "Zombie Hunter" aficionado. I will ask him the best way to keep Zombies from my camp.
As far as bears and raccoons go it's almost impossible when they are hungry but they don't like bad smells. I don't recommend going camping without bathing, as that is just gross, but do pack your dirty socks.
We don't have a big Zombie population here but we do have a large bear population here in Western Pennsylvania. I haven't heard any horror stories about either unless you count bears holding up traffic on the highway a horror story. They think they own the roads.