Sorry about thinking the adapter was one that could have the plug piece changed - seems it's an all-in-one adapter. I did see a guy using one recently that he had bent the prongs on to fit our plugs (not sure how safe...?).
Only do that if you want to ruin your power sockets. Friend goes thru their rentals every tennant change and there are inevitably many many ruined ones if there were asians staying there since they use the same horrid plug as the USA.
Go to a store in NZ and get a legit travel adapter and it will be about as safe as that abortion of a US plug will be.