I have been to the Melbourne Zoo with the 70-300. That was pretty much the only lens I needed on the 7D for the whole visit, except for the 100 Macro 2.8. Like it has been said by popo and Wolfsong, the 100-400L should be good on the 5DIII or the 7D for the bit extra reach.
The 100 Macro is good fun in the reptile section and aquariums. Where you thinking of taking a flash?
With changing lenses, it may not be much of an issue from what I have seen in zoos, generally the things that need the bright lenses are grouped together.
Are you going to take photos around Berlin?
Have just been away with family and caravan and dropped in on this park
http://www.zoossa.com.au/monarto-zoo on the way home. One thing that I was again reminded and not trying to state the obvious, was to keep the iso up, its surprisingly dark in some of the enclosures even on a sunny day and the shutter speed drops right down.
Having a ff and crop sensor gives you great options.

I am still debating on what to do, get a ff like the 6D or another cropped body. I am sick of changing lenses when travelling around and having to change from landscape to wildlife set up
If I wasn`t putting in a new kitchen, the choice would be easy.
hey guys
just thinking aloud, would the 70-200 on the 7D be enough, leaving the 100-400 at home, the low light ability may come in handy?