z 4 a 4 + z 4 a 6 + 3 z 2 a 4 + 3 z 2 a 6 − z 2 a 8 + 1 a 4 + 2 a 6 − 2 a 8 {\displaystyle {\frac {z^{4}}{a^{4}}}+{\frac {z^{4}}{a^{6}}}+{\frac {3z^{2}}{a^{4}}}+{\frac {3z^{2}}{a^{6}}}-{\frac {z^{2}}{a^{8}}}+{\frac {1}{a^{4}}}+{\frac {2}{a^{6}}}-{\frac {2}{a^{8}}}}
