proposition: Lemma zleT_el a b: intp a -> intp b-> a <=z b \/ b <z a.
proof: Proof. move=> ca cb; case: (zleT_ell ca cb). - move=> ->; left. BZo_tac. - by move => [pa _]; left. - by right. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)