a14z−4−5a12z−2−4a12z−4 + 15a10z−2 + 6a10z−4 + 10a10−10z2a8−15a8z−2−4a8z−4−20a8 + 4z4a6 + 10z2a6 + 5a6z−2 + a6z−4 + 10a6 + z4a4