az7−2a3z5 + 3az5−2z5a−1 + a5z3−4a3z3 + 5az3−3z3a−1 + z3a−3 + a5z−4a3z + 3az + a5z−1−2a3z−1 + az−1 + a−1z−1−a−3z−1