expression
not at all inferior to; compare favorably with; even better than
Fixed expression used to assert that something is equal to or surpasses a well-known standard. Often followed by a noun or clause indicating the benchmark. Literary and somewhat formal.
この新作は前作に勝るとも劣らぬ出来だ。
This new work is not at all inferior to the previous one.
彼の演技はプロに勝るとも劣らぬものだった。
His performance was comparable to that of a professional.
A classical Japanese construction combining the verbs 勝る (to excel) and 劣る (to be inferior) with the particles とも (even if) and the archaic negative ぬ. Literally 'even if it excels, it does not fall short', i.e., it is at least equal.