There is no way that this match should be 3-0 to either zoo. Zurich has what is generally considered one of the world's premier elephant complexes, with a decent outdoor area and a phenomenal indoor zone. That's worth at least a point right there. Antwerp has the fantastic 'Buffalo Aviary', as well as the beautiful and historic Egyptian-themed elephant/giraffe/zebra house. That's worth a point right there. So which zoo deserves the 2-1 victory?
Antwerp's Okapi/duiker yards are not very large at all, and the elephant exhibit is puny. Antwerp may have slightly more species (13 to 11), but the exhibits are nothing spectacular whatsoever. Zurich has the excellent Pantanal zone, some average hoofstock yards, and the aforementioned elephant accommodation.
My vote is 2-1 Zurich
That was kinda my train of thought, and I agree with your conclusion. Although Antwerp may have contributed more to the okapi breeding program, Zurich has conttibuted 1.2 million to Lewa conservation in Kenya and Masoala in Madagascar.