I remember seeing outside a veterinary practice a sign including the words ‘Catz and Dogz’ (or vice versa). I didn’t remember the name of the practice, but I knew exactly where it was/is, so was able to search by location online. The practice’s website contains no mention of ‘Catz and Dogz’ and indeed mentions ‘Boarding Dogs and Cats’, but mentions ‘groomz Pet Salon’. Even if my memory of ‘Catz and Dogz’ is faulty, the linguistic issues it raises – pronouncing and spelling final ‘s’ as ‘z‘ – are still valid.
I suspect that many native speakerz of English do not realize that the pronunciation of the ‘s’z on the endz of most plural nounz is actually ‘z’. I didn’t until I starting reading semi-seriously about linguistics. (Or maybe not even then. I didn’t consciously know about the similar alternation of ‘d’ and ‘t’ in past simple verbs until the class component of my first TESOL qualification.) But some wordz stay with the ‘s’ pronunciation. If you say ‘Cats and Dogs’ very slowly and carefully, you will hear that ‘Dogs’ is actually pronounced ‘Dogz’ and ‘grooms’ as ‘groomz’, while ‘Cats’ stays as ‘Cats’.