Consider the following premises. For all z_1, z_1 is a politician if and only if z_1 is a sailor. There is at least one z_1 for which if z_1 were a politician, then z_1 is a sailor. Can we infer the following from them? If we can, name the inference rule being used: For all z_1, the fact that z_1 were a politician does not imply that z_1 is a sailor.
That contradicts the premises. Therefore the answer is no.