\[ \boxed { {x}^{2}{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +x \left ( y \left ( x \right ) \right ) ^{3}+a \left ( y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.507564 (sec), leaf count = 78 \[ \text {Solve}\left [-\frac {i a}{x}=\frac {2 e^{\frac {1}{2} \left (-\frac {i a}{x}-\frac {i}{y(x)}\right )^2}}{2 c_1+\sqrt {2 \pi } \text {erfi}\left (\frac {-\frac {i a}{x}-\frac {i}{y(x)}}{\sqrt {2}}\right )},y(x)\right ] \]
Maple: cpu = 0.141 (sec), leaf count = 82 \[ \left \{ {\it \_C1}+ \left ( x+{\frac {a\sqrt {\pi }\sqrt {2}}{2}{\it Erf} \left ( {\frac {\sqrt {2} \left ( ay \left ( x \right ) +x \right ) }{ 2\,xy \left ( x \right ) }} \right ) {{\rm e}^{{\frac { \left ( ay \left ( x \right ) +x \right ) ^{2}}{2\,{x}^{2} \left ( y \left ( x \right ) \right ) ^{2}}}}}} \right ) {{\rm e}^{-{\frac { \left ( \left ( a-x \right ) y \left ( x \right ) +x \right ) \left ( \left ( x+a \right ) y \left ( x \right ) +x \right ) }{2\,{x}^{2} \left ( y \left ( x \right ) \right ) ^{2}}}}}=0 \right \} \]