It's one of my favorite mid-sized zoos in Germany. Probably not the best zoo to do in winter.
I spent last year 3.5 hours and enjoyed every minute.
Interesting species: crowned sifaka, eastern ring-tailed vontsira, grey langur, white-crowned mangabey, Mitchie's tufted deer, pale golden spiny mouse, Malayan binturong, grey-breasted parakeet, Mitchell's lorikeet, West African pied hornbill (and other hornbill species), western village weaver, white necked raven, yellow gonolek, white-headed duck, Timor yellow-crested cockatoo