It seems that if pot bellied pigs are allowed under the zoning code, a few birds kept as pets, not for eggs, could be worked in. The heck with those neighbors. It doesn't sound like anything you do will improve or impair you relationship with them. Don't let them take up any more of your time. If you can work to change the zoning laws, then you've done something to give yourself peace of mind, no matter who's living next door. Moreover, you've left something for posterity. Think of all the happy children who'll be able to enjoy chickens because of you.