proposition: Lemma zring_plus : forall i j, zring (i + j) [=] zring i[+]zring j.
proof: Proof. intros. astepl (zring_old (i + j)). Step_final (zring_old i[+]zring_old j). 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)