An agreement to sell a property was executed via the CAR forms Listing and Sale agreement. The price was $1,425,000. The Seller stated that 16 units could be developed on the property. The Seller cancelled the agreement a month later, which, according to the contract, makes him responsible to pay the full commission. I informed him of that, and stated that he should just let it expire. However, he then stated that the zoning changed and now the property is worth half million more. An offer was presented at $1,400,000 (a price he countered another person at), and he rejected it and cancelled the agreement. Now he and his attorney are claiming mutual or unilateral mistake bc of the zoning change. We obviously want him to sell it but since he won’t can we make any arguments to obtain a settlement since he violated the contract?