German & New Zealand Dual nationality?

As far as I know Germany generally only allows for one passport. If you want dual citizenship you would need to apply in Germany to keep your German passport first which is called 'Beibehaltungsurkunde' (I think) and you would probably give valid reasons why you would like to keep your German citizenship if you live in New Zealand. Once you have that you can apply for New Zealand citizenship. I think that's how it works, but not 100% sure. I hope this is helpful. Good luck.