To seek the skin from a tiger
To attempt something impossible; refers to a scheme that is difficult to accomplish because it involves hurting one of the involved parties
Negative
向霸权主义者呼吁平等，无异于与虎谋皮 | Xiàng bàquán zhǔyì zhě hūyù píngděng, wúyìyú yǔhǔmóupí
To ask the hegemonists for peace is no different than asking a tiger for its skin
[Source]
要日本帝国主义放弃侵华野心，无异于与虎谋皮 | Yào rìběn dìguó zhǔyì fàngqì qīnhuá yěxīn, wúyìyú yǔhǔmóupí
To ask imperialist Japan to give up its ambition to invade China is impossible and will end in failure
[Source]
None
None
The story below contains a fox and a sheep, while the chengyu itself is about a tiger. The story is accurate -- the chengyu itself evolved over time to refer to a tiger
《太平御览》(Tài Píng Yǔ Lǎn), written by Northern Song Dynasty (北宋 | Běi Sòng | 960 - 1127) author 李昉 (Lǐ Fǎng). The compilation of 1,000 scrolls details the history of the Song Dynasty
During the Zhōu Dynasty (周, 1046 - 256 BC), there lived a man who loved expensive fox skins and valuable food products. All day and all night, he yearned for an obscenely expensive fur-lined coat, and all day and all night, he yearned to be able to have exquisite foods at a sacrificial banquet.
One day, he decided that he simply had to realize his desires. He found a fox den, entered it, and asked the fox within whether he could have his furs. The terrified fox immediately turned around and fled without a word.
Not to be entirely discouraged, the man then went and found a sheep. After some conversation, he asked the sheep whether it would be willing to cut off some its own flesh and give it to him. He hadn't even finished his question before the sheep broke out in a cold sweat and ran off to hide in the forest.