[钻牛角尖 / 鑽牛角尖, zuān niú jiǎo jiānㄗㄨㄢ ㄋㄧㄡˊ ㄐㄧㄠˇ ㄐㄧㄢ] lit. to hone a bull's horn (成语 saw); fig. to waste time on an insoluble or insignificant problem; to bash one's head against a brick wall; a wild goose chase; a blind alley; to split hairs#40406
[对牛弹琴 / 對牛彈琴, duì niú tán qínㄉㄨㄟˋ ㄋㄧㄡˊ ㄊㄢˊ ㄑㄧㄣˊ] to play the lute to a cow (成语 saw); fig. offering a treat to a unappreciative audience; to cast pearls before swine; caviar to the general; to preach to deaf ears; to talk over sb's head#66338
[汗牛充栋 / 汗牛充棟, hàn niú chōng dòngㄏㄢˋ ㄋㄧㄡˊ ㄔㄨㄥ ㄉㄨㄥˋ] lit. enough books to make a pack-ox sweat or to fill a house to the rafters (成语 saw); fig. many books#95529