proposition: Lemma pre_comp_with_z_iso_is_inj' {C : precategory} {a b b' : C} {f : a --> b} (i : is_z_isomorphism f) : ∏ (f' g' : b --> b'), f · f' = f · g' -> f' = g'.
proof: Proof. intros f' g' H. apply (pre_comp_with_z_iso_is_inj (pr2 i)). exact H. Qed.
imports: UniMath.Foundations.PartA UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.Tactics UniMath.CategoryTheory.Core.Categories