I've no definite plans for this year yet, but after smashing my previous record with 100 visits to 48 zoos (only Duisburg & Cologne outside England) and 18 new ones in 2018, if I beat that I'll be very happy!
That's a nice haul for a year (especially the number of new ones), if you near-equal it I'd call it a good year.
The two zoos I've always wanted to visit in the UK are Highland Wildlife Park and Exmoor. I think the latter will be achieved , but HWP may depend on how much of the next list I achieve
HWP is one seriously long haul and pain in the backside to drive to (from Edinburgh). Unless you're going for a full on Scottish jaunt with a few other collections I'd suggest you'd be better spending the energy/money going to the continent.