chingi

Actually we have a fiction Z-apoc world made by fiction writer - Andrei Kruz. And he solved this problem in his books, by making zombies, which killed people (and ate them) stronger and stronger, and called them "morphs". On the late phases of mutations, those ones were extremely fast, and almost invulnerable - and of course there were a lot of them, in intresting places. So you had to be a team of 5 ot 10, to get into such places, because you were always in danger of meeting morphs