\[ y''(x)=2 y(x) \csc ^2(x) \] ✓ Mathematica : cpu = 0.0708253 (sec), leaf count = 67
DSolve[Derivative[2][y][x] == 2*Csc[x]^2*y[x],y[x],x]
\[\left \{\left \{y(x)\to \frac {c_1 \cos (x)}{\sqrt {\cos ^2(x)-1}}+\frac {c_2 \left (-\sqrt {\cos ^2(x)-1}-\cos (x) \log \left (\sqrt {\cos ^2(x)-1}-\cos (x)\right )\right )}{\sqrt {\cos ^2(x)-1}}\right \}\right \}\] ✓ Maple : cpu = 0.283 (sec), leaf count = 50
dsolve(diff(diff(y(x),x),x) = 2/sin(x)^2*y(x),y(x))
\[y \left (x \right ) = \frac {i \sin \left (2 x \right ) \ln \left (\cos \left (2 x \right )+i \sin \left (2 x \right )\right ) c_{2}+\left (-1+\cos \left (2 x \right )\right ) \left (c_{1} \cot \left (x \right )-2 c_{2}\right )}{-1+\cos \left (2 x \right )}\]