\[ y''(x)=-4 y(x) \sin (3 x) \csc ^3(x) \] ✓ Mathematica : cpu = 0.16028 (sec), leaf count = 61
\[\left \{\left \{y(x)\to \sqrt [4]{-\sin ^2(x)} \left (c_1 P_{-\frac {1}{2}+4 i}^{\frac {i \sqrt {47}}{2}}(\cos (x))+c_2 Q_{-\frac {1}{2}+4 i}^{\frac {i \sqrt {47}}{2}}(\cos (x))\right )\right \}\right \}\]
✓ Maple : cpu = 0.231 (sec), leaf count = 38
\[ \left \{ y \left ( x \right ) =\sqrt {\sin \left ( x \right ) } \left ( {\it LegendreQ} \left ( -{\frac {1}{2}}+4\,i,{\frac {i}{2}}\sqrt {47},\cos \left ( x \right ) \right ) {\it \_C2}+{\it LegendreP} \left ( -{\frac {1}{2}}+4\,i,{\frac {i}{2}}\sqrt {47},\cos \left ( x \right ) \right ) {\it \_C1} \right ) \right \} \]