\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) - \left ( 1+2\, \left ( \tan \left ( x \right ) \right ) ^{2} \right ) y \left ( x \right ) =0} \]
Mathematica: cpu = 0.162021 (sec), leaf count = 84 \[ \left \{\left \{y(x)\to \frac {c_1 \sqrt [4]{1-\cos ^2(x)} \sec (x)}{\sqrt [4]{\cos ^2(x)-1}}-\frac {c_2 \sqrt [4]{1-\cos ^2(x)} \sec (x) \left (\cos (x) \sqrt {1-\cos ^2(x)}-\sin ^{-1}(\cos (x))\right )}{2 \sqrt [4]{\cos ^2(x)-1}}\right \}\right \} \]
Maple: cpu = 0.109 (sec), leaf count = 34 \[ \left \{ y \left ( x \right ) ={\frac {{\it \_C1}}{\cos \left ( x \right ) }}+{\frac {{\it \_C2}\, \left ( i\cos \left ( x \right ) \sin \left ( x \right ) +\ln \left ( \cos \left ( x \right ) +i\sin \left ( x \right ) \right ) \right ) }{\cos \left ( x \right ) }} \right \} \]