relevant text in the zombie entry -
Special Attacks: A zombie retains none of the base creature's special attacks.
Wasps have exoskeletons? I would assume this eliminates them as undead skeletons.
So it retains the sting, gains a slam attack, but no poison. I think. And this makes sense; transforming the OP's example from living (ie naturally creating poison for its sting) to undead (ie infusing it with negative energy to create a controlled subject) would skip the life cycle part of poison creation.
If I were the GM, I'd rule that no, RAW zombie giant wasps do not have a poisonous sting, but they gain the slam attack. And I am excited about giant wasp zombies regardless....