−z5a11 + 3z3a11−2za11−2z6a10 + 6z4a10−4z2a10−z7a9 + 4z3a9−za9−4z6a8 + 8z4a8−3z2a8−z7a7−2z5a7 + 6z3a7−4za7 + a7z−1−2z6a6 + 2z2a6−a6−3z5a5 + 4z3a5−4za5 + a5z−1−2z4a4 + z2a4−z3a3 + za3