proposition: Lemma mulz0 : right_zero 0 *%Z.
proof: Proof. by move=> x; rewrite mulzC mul0z. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)