\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =1/2\,{\frac {-\sin \left ( 2\,y \left ( x \right ) \right ) x-\sin \left ( 2\,y \left ( x \right ) \right ) +\cos \left ( 2\,y \left ( x \right ) \right ) {x}^{4}+{x}^{4}}{x \left ( 1+x \right ) }}=0} \]
Mathematica: cpu = 0.493063 (sec), leaf count = 43 \[ \left \{\left \{y(x)\to \tan ^{-1}\left (\frac {-12 c_1+3 x^4-4 x^3+6 x^2-12 x+12 \log (x+1)-25}{12 x}\right )\right \}\right \} \]
Maple: cpu = 0.827 (sec), leaf count = 38 \[ \left \{ y \left ( x \right ) =\arctan \left ( {\frac {3\,{x}^{4}-4\,{x}^ {3}+6\,{x}^{2}+12\,\ln \left ( 1+x \right ) -12\,{\it \_C1}-12\,x}{12\, x}} \right ) \right \} \]