As someone who eagerly collects zoo stuff, I have to say that most UK zoo magazines are shockingly bad: the quality of layout, of writing, and of editorial direction is just dire. ZSL's thing has very limited coverage of the zoos themselves (and what it does have is platitudinous beyond measure). Colchester no longer sends theirs out to members (and, if they did, it web a waste of time, such is the lack of substance to it). Marwell's has all the insight and quality that one might expect from that zoo.
Does Belfast still produce Zoo Crack? And, as far as I know, Banham and Africa Alive still have a 'real' magazine which was, certainly until very recently, as good as anything else in the UK - relatively meaty news about the zoo.