a10z−2 + a10z−4−7a8z−2−4a8z−4−4a8 + 6z2a6 + 15a6z−2 + 6a6z−4 + 14a6−4z4a4−10z2a4−13a4z−2−4a4z−4−16a4 + z6a2 + 2z4a2 + 4z2a2 + 4a2z−2 + a2z−4 + 6a2−z4