∀ {α₁ : Type u_5} {α₂ : Type u_6} {β₁ : Type u_7} {β₂ : Type u_8} [inst : CommMonoid α₁] [inst_1 : CommMonoid α₂]
  [inst_2 : CommMonoid β₁] [inst_3 : CommMonoid β₂] {A₁ : Set α₁} {A₂ : Set α₂} {B₁ : Set β₁} {B₂ : Set β₂}
  {f₁ : α₁ → β₁} {f₂ : α₂ → β₂} {n : ℕ},
  IsMulFreimanIso n A₁ B₁ f₁ → IsMulFreimanIso n A₂ B₂ f₂ → IsMulFreimanIso n (A₁ ×ˢ A₂) (B₁ ×ˢ B₂) (Prod.map f₁ f₂)