\[ \lambda y(x)+y^{(4)}(x)=0 \] ✓ Mathematica : cpu = 0.00589507 (sec), leaf count = 76
\[\left \{\left \{y(x)\to c_1 e^{(-1)^{3/4} \sqrt [4]{\lambda } x}+c_2 e^{-\sqrt [4]{-1} \sqrt [4]{\lambda } x}+c_3 e^{-(-1)^{3/4} \sqrt [4]{\lambda } x}+c_4 e^{\sqrt [4]{-1} \sqrt [4]{\lambda } x}\right \}\right \}\]
✓ Maple : cpu = 0.015 (sec), leaf count = 50
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{-i\sqrt [4]{-\lambda }x}}+{\it \_C2}\,{{\rm e}^{i\sqrt [4]{-\lambda }x}}+{\it \_C3}\,{{\rm e}^{-\sqrt [4]{-\lambda }x}}+{\it \_C4}\,{{\rm e}^{\sqrt [4]{-\lambda }x}} \right \} \]