You Do Need power plug adapter while traveling from Sint Maarten to New Zealand.

Here is Why You Need An Adapter

The outlet and plug type used in New Zealand is I and in Sint Maarten are A and B. This is how they look like.

Sint Maarten

In Sint Maarten, outlets of type A and B are in use.

Type A

Type B

New Zealand

In New Zealand, outlets of type I are in use.

Type I