− a 4 z 8 + a 6 z 6 − 6 a 4 z 6 + 2 a 2 z 6 + 4 a 6 z 4 − 14 a 4 z 4 + 8 a 2 z 4 − z 4 + 5 a 6 z 2 − 13 a 4 z 2 + 11 a 2 z 2 − 2 z 2 + a 6 − 4 a 4 + 5 a 2 − 1 {\displaystyle -a^{4}z^{8}+a^{6}z^{6}-6a^{4}z^{6}+2a^{2}z^{6}+4a^{6}z^{4}-14a^{4}z^{4}+8a^{2}z^{4}-z^{4}+5a^{6}z^{2}-13a^{4}z^{2}+11a^{2}z^{2}-2z^{2}+a^{6}-4a^{4}+5a^{2}-1}