− a 4 z 8 + a 6 z 6 − 6 a 4 z 6 + a 2 z 6 + 4 a 6 z 4 − 13 a 4 z 4 + 4 a 2 z 4 + 5 a 6 z 2 − 12 a 4 z 2 + 6 a 2 z 2 + 2 a 6 − 5 a 4 + 4 a 2 {\displaystyle -a^{4}z^{8}+a^{6}z^{6}-6a^{4}z^{6}+a^{2}z^{6}+4a^{6}z^{4}-13a^{4}z^{4}+4a^{2}z^{4}+5a^{6}z^{2}-12a^{4}z^{2}+6a^{2}z^{2}+2a^{6}-5a^{4}+4a^{2}}
