\[ y'(x)=\frac {\frac {1}{2} x^4 \cos (2 y(x))+\frac {1}{2} x^3 \cos (2 y(x))+\frac {x^4}{2}+\frac {x^3}{2}-\frac {1}{2} \sin (2 y(x))+\frac {1}{2} x \cos (2 y(x))+\frac {x}{2}}{x} \] ✓ Mathematica : cpu = 0.359853 (sec), leaf count = 33
\[\left \{\left \{y(x)\to \tan ^{-1}\left (\frac {4 x^5+5 x^4+10 x^2+10 c_1}{20 x}\right )\right \}\right \}\] ✓ Maple : cpu = 1.783 (sec), leaf count = 29
\[ \left \{ y \left ( x \right ) =\arctan \left ( {\frac {4\,{x}^{5}+5\,{x}^{4}+10\,{x}^{2}+40\,{\it \_C1}}{20\,x}} \right ) \right \} \]