∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Limits.HasZeroObject C]
  [inst_2 : CategoryTheory.HasShift C ℤ] [inst_3 : CategoryTheory.Preadditive C]
  [inst_4 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [hC : CategoryTheory.Pretriangulated C],
  ∀ T ∈ CategoryTheory.Pretriangulated.distinguishedTriangles,
    CategoryTheory.IsIso T.mor₁ → CategoryTheory.Limits.IsZero T.obj₃