az7−a3z5 + 4az5−2z5a−1−3a3z3 + 8az3−6z3a−1 + z3a−3 + a5z−7a3z + 12az−8za−1 + 2za−3 + 2a5z−1−8a3z−1 + 11az−1−6a−1z−1 + a−3z−1 + a5z−3−3a3z−3 + 3az−3−a−1z−3