Hi. I have seen a number of threads from people living in countries where sending a passport overseas to have the visa entered is simply not possible. If you can get a trusted friend or relative who is going overseas to take your passport, this can work well. I would strongly advise pre-arranging this with INZ and also writing a letter of authority for the person to show to Border Control if necessary. If you can take the passports yourself, all well and good.
If not, I have discovered that it is possible to arrange with the New Zealand Consultate or representative in your country to send out your passport for you via their Dipomatic Bag. You can then collect it once it gets returned with the visa. I hope this helps anyone in this position.