Consider the following premises. If Thomas plays tennis, then Thomas is playing squash. For all z_4, z_4 will play tennis if and only if z_4 will play squash. Can we infer the following from them? Thomas is playing squash if and only if Thomas is playing tennis.
 From the fact that for all z_4, z_4 will play tennis if and only if z_4 will play squash we can infer that for all z_4, if z_4 plays squash, then z_4 is playing tennis. From the fact that for all z_4, if z_4 plays squash, then z_4 is playing tennis we can infer that if Thomas plays squash, then Thomas is playing tennis. Finally, from the fact that if Thomas plays squash, then Thomas is playing tennis, and that if Thomas plays tennis, then Thomas is playing squash we can infer that Thomas is playing squash if and only if Thomas is playing tennis. Therefore, the answer is yes.