\[ \boxed { {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left ( x \right ) +f \left ( x \right ) \left ( {x}^{2}{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -2\,x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +2\,y \left ( x \right ) \right ) =0} \]
Mathematica: cpu = 0.081010 (sec), leaf count = 34 \[ \text {DSolve}\left [f(x) \left (x^2 y''(x)-2 x y'(x)+2 y(x)\right )+y^{(3)}(x)=0,y(x),x\right ] \]
Maple: cpu = 0.141 (sec), leaf count = 33 \[ \left \{ y \left ( x \right ) = \left ( \int \!{\it \_C1}+{\it \_C2}\, \int \!{{\rm e}^{-\int \!{x}^{2}f \left ( x \right ) +3\,{x}^{-1} \,{\rm d}x}}\,{\rm d}x\,{\rm d}x+{\it \_C3} \right ) x \right \} \]