But why worry (too much) about misconnecting at AKL? You are on ticket and if you misconnect because incoming flight is late, NZ will take care of you and rebook you on the next WLG flight (I assume that there numerous flights a day). There is absolutely nothing to worry about. Moreover, 2 hours should be more than sufficient to clear immigration and proceed to the domestic flight (admittedly, I have never been to AKL or any experience with transitting there, so I'm not able to tell you if you have to collect bags and check-in again (I assume it though)).
Have a nice trip! (it is very long flights and in Y so just get them over with and enjoy your time in NZ).