\[ x \left (x^2+1\right ) y^{(3)}(x)+3 \left (2 x^2+1\right ) y''(x)-12 y(x)=0 \] ✓ Mathematica : cpu = 0.272014 (sec), leaf count = 104
\[\left \{\left \{y(x)\to \frac {1}{3} c_1 \left (2 x^2+1\right )+\frac {1}{3} c_2 x \sqrt {x^2+1}-\frac {c_3 \left (2 x^2+1\right ) \left (3 \left (x^4+x^2\right ) \tanh ^{-1}\left (\sqrt {x^2+1}\right )-\sqrt {x^2+1} \left (3 x^2+1\right )\right )}{6 \sqrt {x^2+1} \left (2 x^3+x\right )}\right \}\right \}\] ✓ Maple : cpu = 0.372 (sec), leaf count = 60
\[\left \{y \left (x \right ) = \frac {3 c_{2} \sqrt {x^{2}+1}\, x^{2} \arctanh \left (\frac {1}{\sqrt {x^{2}+1}}\right )+2 c_{3} x^{3}+c_{1} \sqrt {x^{2}+1}\, x^{2}-3 c_{2} x^{2}+c_{3} x -c_{2}}{x}\right \}\]