\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) - \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) \cot \left ( x \right ) +y \left ( x \right ) \left ( \sin \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.036005 (sec), leaf count = 19 \[ \left \{\left \{y(x)\to c_1 \cos (\cos (x))-c_2 \sin (\cos (x))\right \}\right \} \]
Maple: cpu = 0.063 (sec), leaf count = 15 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,\sin \left ( \cos \left ( x \right ) \right ) +{\it \_C2}\,\cos \left ( \cos \left ( x \right ) \right ) \right \} \]