a 12 − z 4 a 10 − 7 z 2 a 10 − 6 a 10 + 2 z 6 a 8 + 11 z 4 a 8 + 15 z 2 a 8 + 6 a 8 − z 8 a 6 − 5 z 6 a 6 − 6 z 4 a 6 − 2 z 2 a 6 + z 6 a 4 + 4 z 4 a 4 + 3 z 2 a 4 {\displaystyle a^{12}-z^{4}a^{10}-7z^{2}a^{10}-6a^{10}+2z^{6}a^{8}+11z^{4}a^{8}+15z^{2}a^{8}+6a^{8}-z^{8}a^{6}-5z^{6}a^{6}-6z^{4}a^{6}-2z^{2}a^{6}+z^{6}a^{4}+4z^{4}a^{4}+3z^{2}a^{4}}
