∀ (C : Type u_1) (D : Type u_2) [inst : CategoryTheory.Category.{v_1, u_1} C]
  [inst_1 : CategoryTheory.Category.{v_2, u_2} D] [inst_2 : CategoryTheory.MonoidalCategory C]
  [inst_3 : CategoryTheory.MonoidalCategory.MonoidalRightAction C D] (X X_1 : C) (X_2 : D),
  (((CategoryTheory.MonoidalCategory.MonoidalRightAction.actionAssocNatIso C D).hom.app X).app X_1).app X_2 =
    (CategoryTheory.MonoidalCategory.MonoidalRightActionStruct.actionAssocIso X_2 X X_1).hom