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.

a occhi chiusi, con una mano legata dietro la schiena

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.
È così bravo, potrebbe fare questo lavoro con una mano legata dietro la schiena.
For an experienced chef, making this dish is like doing it with one hand tied behind their back.
Per uno chef esperto, preparare questo piatto è come farlo con una mano legata dietro la schiena.