230v Adapter?

You won't need a voltage converter, but you will need some wall plug adapters.

New Zealand uses what is known as a Type I plug. The adapter will look something like this:

Purchase enough adapters to handle the iPhones, iPads, laptops, hairdryer, razor etc.

Amazon has them, or you can pay 3 times as much at the Airport shops.

The Apple Travel Kit is nice (and expensive), but the downside is that you really only get 1 adapter that will work correctly for the country that you visit. You can buy 5-6 adapters for about half of the cost of the Apple Kit.

Apple power adapters support voltages from 110 to 240 volts. All you should need is a plug adapter to plug your exiting Apple power brick into the New Zealand Wall sockets.

Apple World Travel Adapter Kit - Apple

For third party power adapters consult their documentation to see if they support the NZ voltage and frequency.

Otherwise you would need a power converter.

Australia and NZ to US power converter - Amazon.com