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

Here is Why You Need An Adapter

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

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D

Zambia

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

Type C

Type D

Type G