proposition: Lemma zmaddAC : forall (m : zmodule)(x y z : m), x \+ y \+ z = x \+ z \+ y.
proof: Proof. by move=> M x y z; rewrite -zmaddA [y \+ _]zmaddC zmaddA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finset)