Goal:
    G : t  HI : invariants  n : Z  m : Z
  ============================
   (- n <= m <-> - m <= n)


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