lit. when the snipe and the clam grapple with each other, the fisherman catches them both (idiom); fig. when two sides are locked in dispute, it's often a third party that benefits
trad. 鷸蚌相爭，漁翁得利
Also written 鷸蚌相爭，漁翁得利【yù bàng xiāng zhēng , yú wēng dé lì】