\[ \boxed { 12\, \left ( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) \right ) y \left ( x \right ) -15\, \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}+8\, \left ( y \left ( x \right ) \right ) ^{3}=0} \]
Mathematica: cpu = 0.321041 (sec), leaf count = 43 \[ \left \{\left \{y(x)\to \frac {2304 c_1^2}{\left (3 c_1^2 x^2+6 c_2 c_1^2 x+3 c_2^2 c_1^2+128\right ){}^2}\right \}\right \} \]
Maple: cpu = 1.575 (sec), leaf count = 147 \[ \left \{ -12\,{\frac {y \left ( x \right ) \left ( 8\,\sqrt {y \left ( x \right ) }-{\it \_C1} \right ) \sqrt {8\,y \left ( x \right ) -{\it \_C1} \,\sqrt {y \left ( x \right ) }}}{\sqrt {-24\, \left ( y \left ( x \right ) \right ) ^{3}+3\,{\it \_C1}\, \left ( y \left ( x \right ) \right ) ^{5/2}}{\it \_C1}\,\sqrt {\sqrt {y \left ( x \right ) } \left ( 8\,\sqrt {y \left ( x \right ) }-{\it \_C1} \right ) }}}-x-{\it \_C2}=0, 12\,{\frac {y \left ( x \right ) \left ( 8\,\sqrt {y \left ( x \right ) }- {\it \_C1} \right ) \sqrt {8\,y \left ( x \right ) -{\it \_C1}\,\sqrt {y \left ( x \right ) }}}{\sqrt {-24\, \left ( y \left ( x \right ) \right ) ^{3}+3\,{\it \_C1}\, \left ( y \left ( x \right ) \right ) ^{5/2}}{\it \_C1}\,\sqrt {\sqrt {y \left ( x \right ) } \left ( 8\,\sqrt {y \left ( x \right ) }-{\it \_C1} \right ) }}}-x-{\it \_C2}=0 \right \} \]