Lemma cancel_z_iso {M : precategory} {x y z : M} (f f' : x --> y) (g : z_iso y z) : f · g = f' · g -> f = f'. Proof. intro e. destruct g as [g [g' H]]. apply (post_comp_with_z_iso_is_inj H). assumption. Qed.
Require Import UniMath.Foundations.PartA. Require Import UniMath.Foundations.Propositions. Require Import UniMath.Foundations.Sets. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.CategoryTheory.Core.Categories.