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