If there is an ongoing hot war you are not sending peacekeepers, you are sending mercenaries.

The article says he was asked about if there was a cease fire:

Asked whether New Zealand would be prepared to send peacekeeping troops to Ukraine in the event of any ceasefire, Christopher Luxon told RNZ that was something he would consider.

If the war is over why do you need peacekeepers?

NZ do a lot of peacekeeping operations. In places that were previously at war. What do you think peacekeepers do?