I have searched the internet, but the results may be not as expected. There are many equivalent expressions according to this meaning. As it is below, all of them can be translated into "吃力不讨好". 不讨好的:thankless 她扮演了一个受累不讨好的角色。 She played a thankless role. 费力不讨好的工作 an unthankful task 费力不讨好的工作 a thankless job. 费力不讨好的事一项具有一个荒谬或毁灭性结果的代价很高的任务 A costly undertaking having an absurd or ruinous outcome. 老板总是让我干吃力不讨好的活。 The boss always leaves me to do all the dirty work. 干费力不讨好的事 be a fool to oneself However, there are still some inspiring expressions. Here they are. 吃力不讨好 do a hard but thankless job; carry owls to Athens "carry owls to Athens" means just the same as "in vain" because Athens is prolific of owls.

how about "in vain"徒劳