∀ {α : Type u_1} [inst : AddGroup α] {H : Type u_2} [inst_1 : AddGroup H] {f : α →+ H} (hf : Function.Surjective ⇑f)
  (h h' : H),
  AddMonoidHom.fiberEquivOfSurjective hf h h' =
    (AddMonoidHom.fiberEquivKerOfSurjective hf h).trans (AddMonoidHom.fiberEquivKerOfSurjective hf h').symm