someone could do something with one hand tied behind his/her back

US /ˈsʌm.wʌn kʊd duː ˈsʌm.θɪŋ wɪð wʌn hænd taɪd bɪˈhaɪnd hɪz hɜːr bæk/
UK /ˈsʌm.wʌn kʊd duː ˈsʌm.θɪŋ wɪð wʌn hænd taɪd bɪˈhaɪnd hɪz hɜːr bæk/
"someone could do something with one hand tied behind his/her back" picture
1.

轻而易举, 一只手被绑在背后也能做

to be able to do something very easily, even under difficult circumstances

:
He's so skilled, he could do this job with one hand tied behind his back.
他技术娴熟,即使一只手被绑在背后也能完成这项工作。
For an experienced chef, making this dish is like doing it with one hand tied behind their back.
对于经验丰富的厨师来说,做这道菜就像一只手被绑在背后一样简单。