\[ y'(x)=\frac {x \left (a^3 x^{12}+24 a^2 x^8 y(x)-32 a^2 x^6+192 a x^4 y(x)^2-256 a x^2 y(x)-256 a x^2+512 y(x)^3\right )}{64 a x^4+512 y(x)+512} \] ✓ Mathematica : cpu = 0.315249 (sec), leaf count = 81
\[\left \{\left \{y(x)\to \frac {1}{8} \left (-a x^4-8\right )+\frac {1}{512 \left (\frac {1}{512}-\frac {1}{\sqrt {-262144 x^2+c_1}}\right )}\right \},\left \{y(x)\to \frac {1}{8} \left (-a x^4-8\right )+\frac {1}{512 \left (\frac {1}{512}+\frac {1}{\sqrt {-262144 x^2+c_1}}\right )}\right \}\right \}\] ✓ Maple : cpu = 0.062 (sec), leaf count = 79
\[\left \{y \left (x \right ) = \frac {\left (-\sqrt {-x^{2}+c_{1}}-1\right ) a \,x^{4}-8}{8+8 \sqrt {-x^{2}+c_{1}}}, y \left (x \right ) = \frac {\left (-\sqrt {-x^{2}+c_{1}}+1\right ) a \,x^{4}+8}{-8+8 \sqrt {-x^{2}+c_{1}}}\right \}\]