− z 4 a 8 − 4 z 2 a 8 − 4 a 8 + z 6 a 6 + 6 z 4 a 6 + 11 z 2 a 6 + 6 a 6 − a 4 {\displaystyle -z^{4}a^{8}-4z^{2}a^{8}-4a^{8}+z^{6}a^{6}+6z^{4}a^{6}+11z^{2}a^{6}+6a^{6}-a^{4}}
