\[ x \left (x^2+1\right ) y^{(3)}(x)+3 \left (2 x^2+1\right ) y''(x)-12 y(x)=0 \] ✓ Mathematica : cpu = 0.255438 (sec), leaf count = 106
\[\left \{\left \{y(x)\to \frac {1}{3} c_1 \left (2 x^2+1\right )+\frac {1}{3} c_2 x \sqrt {x^2+1}+\frac {c_3 \left (2 x^2+1\right ) \left (3 x^2+3 \sqrt {x^2+1} x^2 \log (x)-3 \sqrt {x^2+1} x^2 \log \left (\sqrt {x^2+1}+1\right )+1\right )}{6 \left (2 x^3+x\right )}\right \}\right \}\] ✓ Maple : cpu = 0.448 (sec), leaf count = 60
\[ \left \{ y \left ( x \right ) ={\frac {1}{x} \left ( 3\,\sqrt {{x}^{2}+1}{\it Artanh} \left ( {\frac {1}{\sqrt {{x}^{2}+1}}} \right ) {\it \_C2}\,{x}^{2}+{\it \_C1}\,{x}^{2}\sqrt {{x}^{2}+1}+2\,{\it \_C3}\,{x}^{3}-3\,{\it \_C2}\,{x}^{2}+{\it \_C3}\,x-{\it \_C2} \right ) } \right \} \]