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

Here is Why You Need An Adapter

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

Zambia

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

Type C

Type D

Type G

Equatorial Guinea

In Equatorial Guinea, outlets of type C and E are in use.

Type C

Type E