It sure stinks when you have a neighbor who's mission in life seems to be making a nuisance of themselves......I don't know if it would do any good at this point since the zoning people already know your property is under the 4 acre limit but....I would kiss some major rear, I would go to the neighbors dripping with so much sweetness that bees would swarm.....I would ask them if there was ANYTHING you could do to make the situation better for
them and explain how much the horses mean to your family....tell them you would be willing to put up a fence so
they wouldn't be bothered so much ( even though you where going to do the fence anyway
).....apologize for any thing you may have done to upset them....If it meant keeping my pets I would do it....at this point you have nothing to lose.....Good luck in what ever you decide to do....