You Do Need power plug adapter while traveling from Switzerland 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 Switzerland are C and J. This is how they look like.

Switzerland

In Switzerland, outlets of type C and J are in use.

Type C

Type J

Equatorial Guinea

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

Type C

Type E