∀ {C : Type u_4} [inst : CategoryTheory.Category.{u_3, u_4} C] [inst_1 : CategoryTheory.Limits.HasZeroMorphisms C]
  {D : Type u_2} [inst_2 : CategoryTheory.Category.{u_1, u_2} D] [inst_3 : CategoryTheory.Limits.HasZeroMorphisms D]
  {X Y : C} {f : X ⟶ Y} (G : CategoryTheory.Functor C D) [G.PreservesZeroMorphisms],
  CategoryTheory.CategoryStruct.comp
      ((CategoryTheory.Limits.parallelPair (G.map f) 0).map CategoryTheory.Limits.WalkingParallelPairHom.right)
      (CategoryTheory.Iso.refl
          ((CategoryTheory.Limits.parallelPair (G.map f) 0).obj CategoryTheory.Limits.WalkingParallelPair.one)).hom =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Iso.refl
          ((CategoryTheory.Limits.parallelPair (G.map f) 0).obj CategoryTheory.Limits.WalkingParallelPair.zero)).hom
      (((CategoryTheory.Limits.parallelPair f 0).comp G).map CategoryTheory.Limits.WalkingParallelPairHom.right)