proposition: Lemma zify_add_subproof e1 e2 : rval e1 + rval e2 = (zval e1 + zval e2)%:~R.
proof: Proof. by rewrite 2!zifyRingE intrD. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg ssrnum ssrint)