\[ f(x) \cos (a y(x))+g(x) \sin (a y(x))+h(x)+y'(x)=0 \] ✗ Mathematica : cpu = 25.3589 (sec), leaf count = 0 , could not solve
DSolve[Cos[a*y[x]]*f[x] + h[x] + g[x]*Sin[a*y[x]] + Derivative[1][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0 , could not solve
dsolve(diff(y(x),x)+f(x)*cos(a*y(x))+g(x)*sin(a*y(x))+h(x) = 0,y(x))