Just a bit of background: one of my favorite zombie causers is from the Dead Rising video game series. In it, the undead are reanimated by a wasp-like insect that lays eggs in a corpse (I think. It's been a bit). I always thought that was a cool gimmick if nothing else, but something wondrous happened in the third entry in the franchise. A variant of zombie was introduced that was covered in hives of stinging wasps. I thought that was an amazing visual and a great idea.
With that in mind, I've been trying to think about a wasp hive and zombie symbiotic relationship. From the wasps point of view, zombies are free food. Zombies just don't care about wasps. However, I can't think of an actual reason why wasps would put their nests inside a walking corpse that's prone to lunging at living humans.
What benefits would a species of wasp-like insects have to receive so that they make hives in walking-corpse-style zombies?
For the framework of this question, the zombie is a rotting corpse that's being animated by malevolent spirits. It can be intentionally created, but have a nasty tendency to occur naturally on "cursed land". The point is that long term evolution/adaptation on the part of the wasp is possible here.
Also, I'm going to check the box that says only humans can become zombies. That makes this hypothetical setting less awesome, but closes the lid on what would otherwise be a big can of worms.