Nuketown Zombies is only out on XBOX at the moment but should be out on PS3 soon. It has to be downloaded from the store.
I haven't played Zombies too much but it definitely has some freezing issues to be worked out. Anytime you drop to two players from a 3 or 4 player lobby it's going to hard freeze within a round. That's been a problem going back at least to BO1 Acension days. You would think that after year of development they would have resolved that issue.