a 8 ( − z 2 ) − a 8 + a 6 z 4 + 2 a 6 z 2 + a 4 z 4 + 3 a 4 z 2 + 2 a 4 {\displaystyle a^{8}\left(-z^{2}\right)-a^{8}+a^{6}z^{4}+2a^{6}z^{2}+a^{4}z^{4}+3a^{4}z^{2}+2a^{4}}
