∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Limits.HasPullbacks C]
  {X Y Z : C} (f : X ⟶ Z) (g : Y ⟶ Z) {Z_1 : C} (h : Y ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.diagonalObjPullbackFstIso f g).inv
      (CategoryTheory.CategoryStruct.comp
        (CategoryTheory.Limits.pullback.fst (CategoryTheory.Limits.pullback.fst f g)
          (CategoryTheory.Limits.pullback.fst f g))
        (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.snd f g) h)) =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Limits.pullback.fst
        (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.snd g g) g) f)
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.fst g g) h)