You Do Need power plug adapter while traveling from Niue to Zambia.

Here is Why You Need An Adapter

The outlet and plug type used in Zambia are C, D and G and in Niue is I. This is how they look like.

Niue

In Niue, outlets of type I are in use.

Type I

Zambia

In Zambia, outlets of type C, D and G are in use.

Type C

Type D

Type G