费力不讨好

費力不討好
fèilìbùtǎohǎo
arduous and thankless task (idiom); strenuous and unrewarding

CEDICT

Entry Composition

1 费力 fèilì to expend a great deal of effort
2 不 bù
  1. no; not so
  2. (bound form) not; un-
3 讨好 tǎohǎo
  1. to get the desired outcome
  2. to win favor by fawning on sb
  3. to curry favor with
  4. a fruitful outcome to reward one's labor

Related entries

吃力不讨好 chīlìbùtǎohǎo arduous and thankless task (idiom); strenuous and unrewarding
翻译其实是一件吃力不讨好的事，因为一种语言在另一种语言中的对应物藏在往往隐藏在深不可测之处，翻译者需要百般寻觅，而且，挑剔的读者很难糊弄。

In reality, translation is akin to working for peanuts, since the corresponding meaning of something in one language is often hidden in some deep and impenetrable recesses of the other. As a result, the translator is forced to search all over... Never mind that the picky reader is very difficult to fool.

Source: Tatoeba