Do you have a house in NZ? Is it (almost) mortage-free?
Do you and your partner have a good job in NZ?
Do you have kids?
what is the more important to you? lifesyle or career development.
I have done what you want to do. IMHO, NZ has better lifestyle; while OZ offers better opportunities. Afterall, not much difference really. Both My wife and I wouldn't mind to go back and live in NZ again.