\[ \sin (2 x) y'(x)+\sin (2 y(x))=0 \] ✓ Mathematica : cpu = 0.0737002 (sec), leaf count = 45
DSolve[Sin[2*y[x]] + Sin[2*x]*Derivative[1][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to -\frac {1}{2} \arccos (-\tanh (\text {arctanh}(\cos (2 x))+2 c_1))\right \},\left \{y(x)\to \frac {1}{2} \arccos (-\tanh (\text {arctanh}(\cos (2 x))+2 c_1))\right \}\right \}\] ✓ Maple : cpu = 0.521 (sec), leaf count = 105
dsolve(sin(2*x)*diff(y(x),x)+sin(2*y(x)) = 0,y(x))
\[y \left (x \right ) = \frac {\arctan \left (-\frac {2 c_{1} \left (\sin \left (4 x \right )+2 \sin \left (2 x \right )\right )}{-3-c_{1}^{2}+c_{1}^{2} \cos \left (4 x \right )-\cos \left (4 x \right )-4 \cos \left (2 x \right )}, \frac {c_{1}^{2} \cos \left (4 x \right )-c_{1}^{2}+4 \cos \left (2 x \right )+\cos \left (4 x \right )+3}{-3-c_{1}^{2}+c_{1}^{2} \cos \left (4 x \right )-\cos \left (4 x \right )-4 \cos \left (2 x \right )}\right )}{2}\]