proposition: Lemma reverseCommIsoSquare' {M : precategory} {P Q P' Q':M} (f:P'-->P) (g:Q'-->Q) (i:z_iso P' Q') (j:z_iso P Q) : f · j = i · g -> g · z_iso_inv j = z_iso_inv i · f.
proof: Proof. intros l. refine (! _). apply reverseCommIsoSquare. refine (! _). exact l. Qed.
imports: UniMath.Foundations.PartD UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.Notations UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.opp_precat UniMath.CategoryTheory.Limits.Zero UniMath.CategoryTheory.Limits.Opp