\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =1/3\,x \left ( -2+3\,x\sqrt {{x}^{2}+3\,y \left ( x \right ) } \right ) =0} \]
Mathematica: cpu = 0.118515 (sec), leaf count = 31 \[ \left \{\left \{y(x)\to \frac {1}{12} \left (-6 c_1 x^3+9 c_1^2+x^6-4 x^2\right )\right \}\right \} \]
Maple: cpu = 0.172 (sec), leaf count = 22 \[ \left \{ {\it \_C1}+{\frac {{x}^{3}}{2}}-\sqrt {{x}^{2}+3\,y \left ( x \right ) }=0 \right \} \]