−2z5a−1 + 3az3−8z3a−1 + 3z3a−3−a3z + 6az−12za−1 + 8za−3−za−5 + 3az−1−8a−1z−1 + 7a−3z−1−2a−5z−1 + az−3−3a−1z−3 + 3a−3z−3−a−5z−3