Botanicall collection should be easy to establish.
And why would you think that? Why would establishing a great botanical collection be any easier than establishing a great zoological collection? I know collections that struggled for years to obtain certain plant species they wanted.
But of course, I primarly taught on holding those hot species mentioned in the original post, and at the same time, also a great collection of venomous snakes and birds. I did not mentioned other taxa for examples monkeys, since a holding of a bonobo, mostly, is an indicator that the holding zoo has a great collection of primates too..
Rhino, koala, bonobo, venomous snakes and okapi, so practically your favourite animals? How about a great collection of... frogs, non-venomous snakes, crocodilians, rodents, carnivores or insects? Are they less important?
That's a bit much I guess, Arnhem (Burger's) and Apeldoorn (Apenheul) are not part of the Randstad.
You are right, but if one takes these maps into consideration, you could actually take the Netherlands as one metropolitan area. Include the German Ruhrgebiet into this (it's right next to it), and you have a massive urban area boasting over a dozen major collections like Amsterdam, Rotterdam, Rhenen, Arnhem, Duisburg, Dortmund and Gelsenkirche, and many dozens of small and medium sized collections.