2z5a−3−4z3a−1 + 7z3a−3−3z3a−5 + 2az−9za−1 + 12za−3−6za−5 + za−7 + 3az−1−9a−1z−1 + 10a−3z−1−5a−5z−1 + a−7z−1 + az−3−3a−1z−3 + 3a−3z−3−a−5z−3