a9z−1 + a9z−3−3za7−5a7z−1−3a7z−3 + 3z3a5 + 6za5 + 6a5z−1 + 3a5z−3−z5a3−2z3a3−2za3−a3z−1−a3z−3 + z3a−za−az−1