proposition: Lemma mulzA : associative mulz.
proof: Proof. by move=> [] m [] n [] p; rewrite ?NegzE ?(mulnA,mulNz,mulzN,opprK) //= ?mulnA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)