duck soup, like

slang Very easy. Oh please, I've been playing guitar for 20 years—that song is duck soup.

Fig. very easy; an easy thing to do. For Maria, knitting a sweater is duck soup. Jill: This jar is stuck. Could you open it for me? Jane: Sure. Duck soup.

An easily accomplished task or assignment, a cinch to succeed, as in Fixing this car is going to be duck soup. This expression gained currency as the title of a hilarious popular movie by the Marx Brothers (1933). The original allusion has been lost. [Early 1900s]

Extremely simple, easily accomplished. This American colloquialism dates from about 1910, and its origin is no longer known. It gained currency after it became the title of one of the Marx Brothers’ zaniest motion pictures (1933).

Easy to accomplish. The first appearance of the phrase was in a 1902 newspaper cartoon that had nothing to do with ducks. Not then and not now has anybody been able to suggest a likely derivation. If you're interested in an expression that makes sense, try the equivalent, “as easy as falling off a log.”