∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Preadditive C]
  (K : CochainComplex C ℤ) (n : ℤ),
  ((CategoryTheory.shiftFunctorZero (CochainComplex C ℤ) ℤ).inv.app K).f n = (HomologicalComplex.XIsoOfEq K ⋯).hom