\[ \boxed { \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{3}-ax{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +{x}^{3}=0} \]
Mathematica: cpu = 0 (sec), leaf count = 0 \[ \text {Hanged} \]
Maple: cpu = 0.046 (sec), leaf count = 299 \[ \left \{ y \left ( x \right ) =\int \!{-{\frac {i}{12}} \left ( \sqrt {3} \left ( -108\,{x}^{3}+12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x} ^{3} \right ) } \right ) ^{{\frac {2}{3}}}-12\,\sqrt {3}ax-i \left ( -108 \,{x}^{3}+12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) } \right ) ^{{\frac {2}{3}}}-12\,iax \right ) {\frac {1}{\sqrt [3]{-108\,{x}^{3}+12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) }}}}}\,{\rm d}x+{\it \_C1},y \left ( x \right ) =\int \!{{ \frac {i}{12}} \left ( \sqrt {3} \left ( -108\,{x}^{3}+12\,\sqrt {-3\,{x }^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) } \right ) ^{{\frac {2}{3}} }-12\,\sqrt {3}ax+i \left ( -108\,{x}^{3}+12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) } \right ) ^{{\frac {2}{3}}}+12 \,iax \right ) {\frac {1}{\sqrt [3]{-108\,{x}^{3}+12\,\sqrt {-3\,{x}^{3 } \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) }}}}}\,{\rm d}x+{\it \_C1},y \left ( x \right ) =\int \!{\frac {1}{6} \left ( \left ( -108\,{x}^{3}+ 12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) } \right ) ^{{\frac {2}{3}}}+12\,ax \right ) {\frac {1}{\sqrt [3]{-108\,{ x}^{3}+12\,\sqrt {-3\,{x}^{3} \left ( 4\,{a}^{3}-27\,{x}^{3} \right ) }} }}}\,{\rm d}x+{\it \_C1} \right \} \]