∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Preadditive C]
  {S₁ S₂ : CategoryTheory.ShortComplex C} {φ₁ φ₂ : S₁ ⟶ S₂} (self : CategoryTheory.ShortComplex.Homotopy φ₁ φ₂) {Z : C}
  (h : S₂.X₂ ⟶ Z),
  CategoryTheory.CategoryStruct.comp self.h₀ (CategoryTheory.CategoryStruct.comp S₂.f h) =
    CategoryTheory.CategoryStruct.comp 0 h