Consider the following premises. forall z: R(z) <-> S(z). exists z: R(z) or ~S(z). Can we infer forall z: ~(R(z) -> S(z)) from them?
 From exists z: R(z) or ~S(z) we can infer exists z: S(z) -> R(z). Finally, from forall z: R(z) <-> S(z) we can infer forall z: R(z) -> S(z), which contradicts forall z: ~(R(z) -> S(z)). Therefore, the answer is no.