I did not know there are eastern gorillas in human care, and several tens!
I agree that it would be best for the gorillas themselves if foreign zoos got them as breeding loans. Currently they are in some orphanages in Africa, where they are vulnerable to diseases, civil disorder and uncertain funding at least as much as wild gorillas. However it looks like neither wolds zoos nor these orphanages are interested in such a plan. Western zoos have enough zoo-bred western gorillas, orphanages have mentality from 50 years ago - before the idea of breeding plans existed and nature was great and safe.