So often people on the forums designate Yellow Labs as one of the relatively peaceful Mbuna.
I have never found that to be true.
One of the most aggressive Mbuna I've ever kept was a male Yellow Lab like yours.
Rehoming an aggressive Mbuna rarely solves anything. The strongest remaining subordinate male usually steps up to be just as aggressive as the original troublemaker.
Two ways to go. Either over populate the tank with many more Yellow Labs & hope for a stalemate between the males, or stock a new group of less territorial Mbuna. I had good luck with Rusties.