Depending on the rest of the article design, that may be fine or it may risk fur getting caught in the zip. I have occasional trouble with my own body hair in zip.
I don't know the terms of art so I can't google for a picture of the "good" design, but it would have a wide strip of fabric behind the zip that would ensure no fur gets near the zip mechanism.
fur may stuck into it. And if zipper gets stuck for whatever reason the dog may not like sitting for the prolonged time while you're trying to unstuck it. Of course it all depends on specific circumstances, and it is definitely great that it works for your dog.
A garment with zipper also requires much better fitting - which giving dog shapes variations may be a tall order - than say with Velcro where usually there is some latitude, and with Velcro it is much easier to make adjustment by moving it a bit if needed while making adjustment with zipper looks daunting.
