\[ \boxed { 3\,{x}^{2} \left ( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) \right ) ^{2}-2\, \left ( 3\,x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +y \left ( x \right ) \right ) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +4\, \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.006001 (sec), leaf count = 24 \[ \left \{\left \{y(x)\to \frac {c_1^2 x^2}{c_2}+c_1 x+c_2\right \}\right \} \]
Maple: cpu = 0.234 (sec), leaf count = 32 \[ \left \{ y \left ( x \right ) ={x}^{{\frac {2\,\sqrt {3}}{3}}}{\it \_C1} \,x,y \left ( x \right ) ={\frac {{{\it \_C1}}^{2}{x}^{2}}{{\it \_C2}}}+ {\it \_C1}\,x+{\it \_C2} \right \} \]