Consider the following premises. exists z: W(z) <-> T(z). forall z: W(z) <-> T(z). Can we infer exists z: T(z) <-> W(z) from them?
 From exists z: W(z) <-> T(z) we can infer exists z: W(z) -> T(z). From forall z: W(z) <-> T(z) we can infer forall z: T(z) -> W(z). Finally, from forall z: T(z) -> W(z), exists z: W(z) -> T(z) we can infer exists z: T(z) <-> W(z). Therefore, the answer is yes.