Good point, Andrew! I am certain that two Knights can do the job. In fact, King and just about any two pieces should be able to force stalemate. I have examined the Wildebeest.zrf and discovered the line:
(loss-condition (White Black) (checkmated King))
So Zillions was not even trying to stalemate the Black King. When this ZRF has been corrected, we should be able test the endgame King and Wildebeest against King.
(loss-condition (White Black) (checkmated King))
So Zillions was not even trying to stalemate the Black King. When this ZRF has been corrected, we should be able test the endgame King and Wildebeest against King.