I think it sounds like a good idea if you put Zoe away when he comes over. Personally I don't like shock collars, I would never want to hurt my dogs, ever. I have never even used "choke" collars before, but that is just my opinion.

If your ex mentions shock collars again maybe you could tell him that they can cause a myriad of other behavioral problems, and using positive reinforcement is probably easier in the long run! Using shocks too liberally can cause learned helplessness, and I know if I used something like that on Adele (who is a very soft, in some ways timid dog) she would probably skulk around the house fearing a shock from somewhere. Also, probably shock collars are expensive, so if your ex is willing to pay for that, maybe he can put the money towards a good class instead!