Fahim has grown up in a good social group in Zurich and after that, lived in a bachelor group with another young bull. Almost all asian bulls with a similar social background do breed without any problems! And according to the Rotterdam Zoo, Fahim has actually mated with Faya and Trong Nhi, so there are no problems with his abilities as breeding bull. However, he might be too energetic for the facilities in Blijdorp. The bull paddock is very small and if I understand it correctly, the females are nervous if he is around them too long so that he cant share the big enclosure with them every day.
Regarding Munster, Ratna is way too old for a first pregnancy. And Corny got pregnant a few years ago in the same social group, so I very much doubt any social problems among the females are the reason why she hasnt had another calf. Social problems can be a reason why a female stopps cycling, but that AI was attempted shows that she actually has a cycle. Failure of one (or two or even three) AI attempts is no proof that something is wrong with the females! Many females need a year or two to get pregnant, but AI is so expensive and difficult to organize to do it more then a few times. I think Corny will have a good chance to get pregnant again if another bull who has sexual interest in her is brought in.
It is very strange that Alex lost interest in the females in Munster; he had been such a relieable breeding bull in the past and mated with all females in the group in serveral zoos (Rotterdam, Antwerp and Amersfoort). And he did mate with Corny in the passt. I hope he has no underlying health problems.