Goal:
    z : Z  z0 : Z  H : (z <= z0)%Z  H0 : (z0 <= z)%Z
  ============================
   (Some z = Some z0)


DEBUG:Going to execute:
intros; Zify.zify_pre_hook; zify_elim_let; zify_op;
            Zify.zify_iter_specs