Consider the following premises. forall z_2: R(z_2) <-> S(z_2). forall z_2: R(z_2) or ~S(z_2). Can we infer forall z_2: R(z_2) <-> S(z_2) from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.