∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Preadditive C]
  {S : CategoryTheory.ShortComplex C} (self : S.Splitting) {Z : C} (h : S.X₁ ⟶ Z),
  CategoryTheory.CategoryStruct.comp S.f (CategoryTheory.CategoryStruct.comp self.r h) = h