I did a 9-day zootrip in the Netherlands last year. I will post a little overview here soon. Blijdorp and Burgers' are must see. You can The Netherlands compare with Germany: many good traditional zoos in the larger cities with very often modern enclosures and interesting collections + a lot of small but well equiped zoos in smaller towns.
In Belgium:
- Antwerp: historical and beautifull landscaped zoo with an interesting collection: eastern and mountain gorilla, king pinguin, tamandua, aardvark, ceylon hulman, spectacled bear, civet, african buffalo, mandrill, 7 species of guan, 6 species of turaco, okapi, takin, anoa, babirussa, vischaja, javan langur, owl-faced guenon, malayan tapir, hippo, etc. Very modern reptile house and nocturama. Enclosures for great apes and cats are too small. They built a new lion enclosure and paddocks for babirussa, anoa and okapi
- Planckendael (Mechelen, 20 min by train from Antwerp): wooded zoo with african village (bonobo, secretary bird), rare giraffes, indian rhino and lion, wombat, koala, echidna, etc. They built a new elephant enclosure.
- Parc Daiza (former Paradisio): impressive collection of birds of prey, shoebill, many rare cranes, kiang. No carnivores. Very nice chinese and indonesian section.
In Germany close to the Dutch border:
- Köln: excellent zoo with strong focus on apes and monkeys (douc, bonobo, several lemur species and south american callithrix), new hippoaquarium and large elephant enclosure. Also good collection of turaco, reptiles, socorro dove, tree kangoroo, etc.
- Duisburg: as already mentioned above, many rare species
- Dortmund: extensive south american collection (tamandua, etc.)
- Wuppertal: many rare species (king cheetah, peruvian cock of the rock, harpy)