∀ {R₁ R₂ R₃ R₄ : Type u₁} [inst : CommRing R₁] [inst_1 : CommRing R₂] [inst_2 : CommRing R₃] [inst_3 : CommRing R₄]
  (f₁₂ : R₁ →+* R₂) (f₂₃ : R₂ →+* R₃) (f₃₄ : R₃ →+* R₄),
  CategoryTheory.CategoryStruct.comp (ModuleCat.extendScalarsComp (f₂₃.comp f₁₂) f₃₄).hom
      (CategoryTheory.CategoryStruct.comp
        (CategoryTheory.Functor.whiskerRight (ModuleCat.extendScalarsComp f₁₂ f₂₃).hom (ModuleCat.extendScalars f₃₄))
        (CategoryTheory.CategoryStruct.comp
          ((ModuleCat.extendScalars f₁₂).associator (ModuleCat.extendScalars f₂₃) (ModuleCat.extendScalars f₃₄)).hom
          (CategoryTheory.CategoryStruct.comp
            ((ModuleCat.extendScalars f₁₂).whiskerLeft (ModuleCat.extendScalarsComp f₂₃ f₃₄).inv)
            (ModuleCat.extendScalarsComp f₁₂ (f₃₄.comp f₂₃)).inv))) =
    CategoryTheory.CategoryStruct.id (ModuleCat.extendScalars (f₃₄.comp (f₂₃.comp f₁₂)))