There is not really a way to do this for individual caches. Traveling caches and various other oddities can be excluded via a bookmark list of such things that Geocaching HQ keeps and that are by default excluded from statistics. That's not really relevant here, though, since the cache in question is just a regular multi that happens to have stages that are very far in between. If you don't feel that you should have an NZ find, what you can do is to remove your log for this cache. Do note, however, that that would not remove your souvenir for NZ - to get rid of that you would need to talk to Geocaching HQ support.
