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