proposition: Lemma zring_diff : forall m n : nat, zring (m - n) [=] nring m[-]nring n.
proof: Proof. intros; Step_final (zring_old (m - n)). Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)