\[ y'(x)=\frac {x \left (a^3 x^{12}+24 a^2 x^8 y(x)-32 a^2 x^6+192 a x^4 y(x)^2-256 a x^2 y(x)-256 a x^2+512 y(x)^3\right )}{64 a x^4+512 y(x)+512} \] ✓ Mathematica : cpu = 0.0231587 (sec), leaf count = 81
\[\left \{\left \{y(x)\to \frac {1}{8} \left (-a x^4-8\right )+\frac {1}{512 \left (\frac {1}{512}-\frac {1}{\sqrt {c_1-262144 x^2}}\right )}\right \},\left \{y(x)\to \frac {1}{8} \left (-a x^4-8\right )+\frac {1}{512 \left (\frac {1}{\sqrt {c_1-262144 x^2}}+\frac {1}{512}\right )}\right \}\right \}\]
✓ Maple : cpu = 0.055 (sec), leaf count = 80
\[ \left \{ y \left ( x \right ) =-{\frac {1}{8} \left ( \sqrt {-{x}^{2}+{\it \_C1}}a{x}^{4}-a{x}^{4}-8 \right ) \left ( -1+\sqrt {-{x}^{2}+{\it \_C1}} \right ) ^{-1}},y \left ( x \right ) =-{\frac {1}{8} \left ( \sqrt {-{x}^{2}+{\it \_C1}}a{x}^{4}+a{x}^{4}+8 \right ) \left ( 1+\sqrt {-{x}^{2}+{\it \_C1}} \right ) ^{-1}} \right \} \]