\[ y''(x)+y(x) \left (-2 \tan ^2(x)-1\right )=0 \] ✓ Mathematica : cpu = 0.196571 (sec), leaf count = 58
DSolve[(-1 - 2*Tan[x]^2)*y[x] + Derivative[2][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to \frac {1}{2} c_2 \sec (x) \left (2 \arctan \left (\frac {\cos (x)}{\sqrt {1-\cos ^2(x)}-1}\right )-\cos (x) \sqrt {1-\cos ^2(x)}\right )+c_1 \sec (x)\right \}\right \}\] ✓ Maple : cpu = 0.172 (sec), leaf count = 28
dsolve(diff(diff(y(x),x),x)-(1+2*tan(x)^2)*y(x)=0,y(x))
\[y \left (x \right ) = \sec \left (x \right ) \left (i \sin \left (x \right ) \cos \left (x \right ) c_{2}+\ln \left (\cos \left (x \right )+i \sin \left (x \right )\right ) c_{2}+c_{1}\right )\]