\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =1/2\,{\frac {-\sin \left ( 2\,y \left ( x \right ) \right ) +x\cos \left ( 2\,y \left ( x \right ) \right ) +\cos \left ( 2\,y \left ( x \right ) \right ) {x}^{3}+\cos \left ( 2\,y \left ( x \right ) \right ) {x}^{4}+x+{x}^{3}+{x}^{4}}{x}}=0} \]
Mathematica: cpu = 0.150519 (sec), leaf count = 33 \[ \left \{\left \{y(x)\to \tan ^{-1}\left (\frac {10 c_1+4 x^5+5 x^4+10 x^2}{20 x}\right )\right \}\right \} \]
Maple: cpu = 1.669 (sec), leaf count = 29 \[ \left \{ y \left ( x \right ) =\arctan \left ( {\frac {4\,{x}^{5}+5\,{x}^ {4}+10\,{x}^{2}+40\,{\it \_C1}}{20\,x}} \right ) \right \} \]