✓ Mathematica : cpu = 0.879978 (sec), leaf count = 31
DSolve[Cos[x] + Cos[x + y[x]] + Sin[x*y[x]]*y[x] + (Cos[x + y[x]] - Sin[y[x]] + x*Sin[x*y[x]])*Derivative[1][y][x] == 0,y[x],x]
✓ Maple : cpu = 0.195 (sec), leaf count = 22
dsolve((x*sin(x*y(x))+cos(y(x)+x)-sin(y(x)))*diff(y(x),x)+y(x)*sin(x*y(x))+cos(y(x)+x)+cos(x) = 0,y(x))