the island with the B/W lemurs is not accessible to the public, the other lemur islands are indeed walk through.
The only other zoo in Belgium that I know with a walk through- exhibit is Family park Harry Malter in Gent. their ringtailed lemurs have an accessible greenhouse.
I indeed remember 1 B/W lemur being kicked out of the group and living on the island of the red ruffed lemurs. But essentially the B/W lemurs as a group have a separate island that is not accessible.