with one hand tied behind back(do something) with one hand tied behind (your) back
to do something very easily.
Cleaning your bike chain is so simple a chimp could do it with one hand tied behind its back.
with one hand tied behind (one's) back
Easily, nearly without having to try at all. I'm a professional musician, so that song is hardly a challenge—I could play it with one hand tied behind my back!
with one hand tied behind one's back
and with both hands tied behind one's back
Fig. even if under a handicap; easily. I could put an end to this argument with one hand tied behind my back. John could do this job with both hands tied behind his back.