In Singles, Quash is utterly useless, as Prankster would make Murkrow go first anyways, which destroys the purpose of the move.
In Doubles/Triples, Quash can be helpful if your Pokemon can neutralize a threat before they can attack. For example, if there was a Mega Kangaskhan on the opposing side, you can use Quash on it and have your partner burn it or outright OHKO it with a fighting move.
Otherwise, Quash was little use, and you're better off using other moves with Prankster.
