\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) ={\frac {{x}^{2} \left ( 3\,x+\sqrt {-9\,{x}^{4}+4\, \left ( y \left ( x \right ) \right ) ^{3}} \right ) }{ \left ( y \left ( x \right ) \right ) ^{2}}}=0} \]
Mathematica: cpu = 0 (sec), leaf count = 0 \[ \text {Hanged} \]
Maple: cpu = 0.156 (sec), leaf count = 36 \[ \left \{ \int _{{\it \_b}}^{y \left ( x \right ) }\!{{{\it \_a}}^{2}{ \frac {1}{\sqrt {-9\,{x}^{4}+4\,{{\it \_a}}^{3}}}}}\,{\rm d}{\it \_a}- {\frac {{x}^{3}}{3}}-{\it \_C1}=0 \right \} \]