∀ {α : Type u_2} {β : Type u_4} {γ : Type u_1} {δ : Type u_3} [inst : MeasurableSpace α] [inst_1 : MeasurableSpace β]
  [inst_2 : MeasurableSpace γ] [inst_3 : MeasurableSpace δ] (ab : α ≃ᵐ β) (cd : γ ≃ᵐ δ),
  Measurable (Sum.map ⇑ab ⇑cd.toEquiv)