It most likely won't be considered back to back ticketing. By the time you reach NZ with your first set of tickets, you probably will be spending more days than the minimum stay requirements so you should be okay.
Besides, no agent would bother doing a tedious task of checking back-to-backs on a round the world itinerary.

BTW, do you know any New Zealand travel agent that's good in round the world fares? Particularly, I'm looking for an agent that handles Air NZ + TG RTW fares ex-AKL. Thanks.