− a 12 + z 2 a 10 + a 10 − z 2 a 8 − 2 a 8 + 2 z 4 a 6 + 6 z 2 a 6 + 3 a 6 + z 4 a 4 + 2 z 2 a 4 {\displaystyle -a^{12}+z^{2}a^{10}+a^{10}-z^{2}a^{8}-2a^{8}+2z^{4}a^{6}+6z^{2}a^{6}+3a^{6}+z^{4}a^{4}+2z^{2}a^{4}}
