Seems like a totally normal dog interaction. In fact, I would be more concerned about the dogs who lack the social skills to politely move away when your dog gives such clear and appropriate signals. I WISH my dog-selective dog was this lenient
I would recommend praising Copper after ALL interactions and immediately giving him a few treats... when the other dog is safely out of your space, of course! This probably won't teach him to love other dogs. But you are at least associating other dogs and greetings with positive outcomes.
When I first started reading your post I was thinking to write 'only bring Zoe to populated areas' but honestly Copper sounds fine. He might not love other dogs but it sounds like he enjoys being out with you and he isn't totally overwhelmed by dog greetings. He just would rather move on, is all.