Hi there! I'm on my second year of IB and I've received offers for Zoology from Bristol and Sheffield. I also have interviews with Manchester and Leeds.
I'm delighted that you're interested in Zoology too!
Personally, I chose SL Maths despite not being very good at Maths precisely because I didn't want to limit myself too much. Currently, I spend around 5 hours (outside lesson time) a week revising Maths, but I'm still only managing a 6 at most.
With hard work, a 5 or 6 should be manageable but you need to consider if it's worth it to devote so much time to one single subject. Right now, I barely have time for other subjects.
Look, I don't even study chemistry AT ALL. I'm still getting offers for Zoology and I doubt Maths is as relevant to Biology/Zoology as Chemistry.
Look at the requirements for Biology/Zoology at different unis. In my case, I've had to avoid unis that require two hard sciences/maths at HL. For example, Imperial.
Instead, I went for unis that accept Biology and Geography at HL. For example, Bristol. As long as you have Biology and another hard science or secondary science subject at HL, you will meet the minimum requirements. But unfortunately, someone doing SL or HL Maths will have an advatage over you. Just like how everyone who's doing chemistry will have an advatage over me, but I'm still getting offers from great unis.
Good luck with your decision!