\[ \left (27 x^2+4\right ) y''(x)+27 x y'(x)-3 y(x)=0 \] ✓ Mathematica : cpu = 0.163952 (sec), leaf count = 103
\[\left \{\left \{y(x)\to c_1 \cosh \left (\frac {\sqrt {-27 x^2-4} \tan ^{-1}\left (\frac {3 x}{\sqrt {-9 x^2-\frac {4}{3}}}\right )}{3 \sqrt {27 x^2+4}}\right )+i c_2 \sinh \left (\frac {\sqrt {-27 x^2-4} \tan ^{-1}\left (\frac {3 x}{\sqrt {-9 x^2-\frac {4}{3}}}\right )}{3 \sqrt {27 x^2+4}}\right )\right \}\right \}\] ✓ Maple : cpu = 0.029 (sec), leaf count = 47
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,\sin \left ( {\frac {1}{3}\arctan \left ( 3\,{\frac {\sqrt {3}x}{\sqrt {-27\,{x}^{2}-4}}} \right ) } \right ) +{\it \_C2}\,\cos \left ( {\frac {1}{3}\arctan \left ( 3\,{\frac {\sqrt {3}x}{\sqrt {-27\,{x}^{2}-4}}} \right ) } \right ) \right \} \]