\[ \boxed { \left ( ay \left ( x \right ) -{x}^{2} \right ) \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}+2\,xy \left ( x \right ) \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}- \left ( y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 30.550379 (sec), leaf count = 41 \[ \text {DSolve}\left [\left (a y(x)-x^2\right ) y'(x)^2+2 x y(x) y'(x)^2-y(x)^2=0,y(x),x\right ] \]
Maple: cpu = 2.044 (sec), leaf count = 0 \[ \text {could not solve} \]