− z 2 a 12 − a 12 + 3 z 4 a 10 + 6 z 2 a 10 + 3 a 10 − 2 z 6 a 8 − 7 z 4 a 8 − 11 z 2 a 8 − 6 a 8 + 5 z 4 a 6 + 11 z 2 a 6 + 5 a 6 + z 4 a 4 + z 2 a 4 {\displaystyle -z^{2}a^{12}-a^{12}+3z^{4}a^{10}+6z^{2}a^{10}+3a^{10}-2z^{6}a^{8}-7z^{4}a^{8}-11z^{2}a^{8}-6a^{8}+5z^{4}a^{6}+11z^{2}a^{6}+5a^{6}+z^{4}a^{4}+z^{2}a^{4}}