Can I offer some advice?
-Calculate in money for hotel, public transport (including local trams, buses etc.) to the zoo(s) and back, food, souvenirs etc.; an EUR 70 minimum is rather unlikely to be enough on a longer run, even if living a shoestring budget lifestyle (which isn't the way to go on such a zoo fun journey...)
-Travelling with trains in Europe is all nice and fine, but more and more unreliable; even the famously punctual German "Deutsche Bahn" is nowadays far from punctual, and rather expensive. Avoid changing trains if possible, as this might leave you stranded in the middle of nowhere if something goes awry.
-Don't try to squeeze in too much at once. The Netherlands are a good spot to start with, as several great zoos are located pretty closeby to each other. However, be also aware that the Dutch price standard for almost everything is currently one of the highest in the EU. You're going to spend more money-and that faster than You can imagine...From the Netherlands, it's only a rather short trip to the North Rhine-Westphalia area of Germany; probably the highest concentration of larger zoos within closest distance to each other in Europe-except mentioned Netherlands. Zoos like Cologne, Duisburg and Wuppertal have several "last of their kind' husbandries to offer, among others Boto, Saiga, Douc Langur, Red Howler Monkey, King Bird of Paradise etc. etc. You could thus see more zoos on the way instead of having to scamper from one to another.
Another route I can recommend: East Germany (Berlin, Leipzig, Dresden, Halle) to the Czech Republic (Chomutov, Prague, Dvur Kralove...) and from there to Austria (Vienna). Great zoos and usually it's cheaper. Instead of trains, I'd recommend travelling with
, STUDENT AGENCY BUS, STUDENT AGENCY, STUDENT AGENCY ONLINE, BOOKING, PRAGUE
Hope I could help.