Consider the following premises. forall z_3: S_3(z_3). exists z_3: Q_1(z_3) <-> S_3(z_3). Can we infer exists z_3: Q_1(z_3) from them?
 From exists z_3: Q_1(z_3) <-> S_3(z_3) we can infer exists z_3: S_3(z_3) -> Q_1(z_3). Finally, from exists z_3: S_3(z_3) -> Q_1(z_3), forall z_3: S_3(z_3) we can infer exists z_3: Q_1(z_3). Therefore, the answer is yes.