Consider the following premises. For all z_3, z_3 will climb a mountain if and only if z_3 will play squash. There is at least one z_3 for which z_3 will play squash if and only if z_3 will read a book. For all z_3, z_3 will not read a book. Can we infer the following from them? For all z_3, z_3 will climb a mountain.
 From the fact that there is at least one z_3 for which z_3 will play squash if and only if z_3 will read a book we can infer that there is at least one z_3 for which if z_3 plays squash, then z_3 is reading a book. From the fact that there is at least one z_3 for which if z_3 plays squash, then z_3 is reading a book, and that for all z_3, z_3 will not read a book we can infer that there is at least one z_3 for which z_3 will not play squash. Finally, from the fact that for all z_3, z_3 will climb a mountain if and only if z_3 will play squash, and that there is at least one z_3 for which z_3 will not play squash we can infer that there is at least one z_3 for which z_3 will not climb a mountain, which contradicts that For all z_3, z_3 will climb a mountain. Therefore, the answer is no.