∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.HasShift C ℤ]
  [inst_2 : CategoryTheory.Preadditive C] (T : CategoryTheory.Pretriangulated.Triangle C)
  (motive : T.mor₁ = 0 ∧ T.mor₃ = 0 → Prop) (h : T.mor₁ = 0 ∧ T.mor₃ = 0),
  (∀ (h₁ : T.mor₁ = 0) (h₃ : T.mor₃ = 0), motive ⋯) → motive h