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