\[ y'(x)=\frac {\frac {1}{2} x^4 \cos (2 y(x))+\frac {x^4}{2}+\frac {1}{2} x^3 \cos (2 y(x))+\frac {x^3}{2}-\frac {1}{2} \sin (2 y(x))+\frac {1}{2} x \cos (2 y(x))+\frac {x}{2}}{x} \] ✓ Mathematica : cpu = 0.351119 (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 = 2.522 (sec), leaf count = 29
\[y \relax (x ) = \arctan \left (\frac {4 x^{5}+5 x^{4}+10 x^{2}+40 c_{1}}{20 x}\right )\]