\[ -\cot (x) y'(x)+y''(x)+y(x) \sin ^2(x)=0 \] ✓ Mathematica : cpu = 0.0273901 (sec), leaf count = 19
\[\{\{y(x)\to c_1 \cos (\cos (x))-c_2 \sin (\cos (x))\}\}\] ✓ Maple : cpu = 0.333 (sec), leaf count = 15
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,\sin \left ( \cos \left ( x \right ) \right ) +{\it \_C2}\,\cos \left ( \cos \left ( x \right ) \right ) \right \} \]