鹬yù蚌bàng相xiāng争zhēng

Literal: the snipe and the clam struggle with each other
Figurative: When two sides lock horns in a stubborn quarrel and neither gives way, a third party walks off with the prize. It warns that fighting among equals only benefits the outsider waiting on the sidelines.

Where does 鹬蚌相争 come from?

During the Warring States period, the state of Zhao was about to attack the state of Yan. The advisor Su Dai went before the king of Zhao and described a scene: a clam had opened its shell to bask in the sun when a snipe swooped down to peck at its flesh; the clam snapped shut and trapped the bird's beak. Neither would let go: the snipe said "if it does not rain today or tomorrow, there will be a dead clam," and the clam replied "if I do not release you today or tomorrow, there will be a dead bird." As they wrangled, a fisherman came by and carried both off with no effort at all. Su Dai's point was that if Zhao and Yan exhausted each other in war, they would simply hand victory to the mighty state of Qin, and the king of Zhao called off the attack.

Source (出处): 《战国策·燕策》

How is 鹬蚌相争 used? Two examples

你nǐ们men两liǎng家jiā公gōng司sī鹬yù蚌bàng相xiāng争zhēng，最zuì后hòu赚zhuàn到dào钱qián的de是shì别bié人rén。
Your two companies are at each other's throats, and in the end it's someone else who pockets the money.
兄xiōng弟dì俩liǎ为wèi了le房fáng子zi鹬yù蚌bàng相xiāng争zhēng，结jié果guǒ让ràng亲qīn戚qi占zhàn了le便pián宜yi。
The two brothers fought tooth and nail over the house, and in the end a relative was the one who came out ahead.

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