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