\[ y''(x)-h\left (y'(x),a x+b y(x)\right )=0 \] ✗ Mathematica : cpu = 0.383215 (sec), leaf count = 0 , could not solve
DSolve[-h[Derivative[1][y][x], a*x + b*y[x]] + Derivative[2][y][x] == 0, y[x], x]
✓ Maple : cpu = 0.232 (sec), leaf count = 115
\[\left \{y \left (x \right ) = \mathit {ODESolStruc} \left (-\frac {-\textit {\_a} b +\left (c_{1}+\int \textit {\_}b\left (\textit {\_a} \right )d \textit {\_a} \right ) a}{b}, \left [\left \{\frac {d}{d \textit {\_a}}\mathrm {\_}\mathrm {b}\left (\textit {\_a} \right )=-\textit {\_}b\left (\textit {\_a} \right )^{3} h \left (\frac {-a \textit {\_}b\left (\textit {\_a} \right )+b}{b \textit {\_}b\left (\textit {\_a} \right )}, \textit {\_a} b \right )\right \}, \left \{\textit {\_a} =\frac {a x +b y \left (x \right )}{b}, \textit {\_}b\left (\textit {\_a} \right )=\frac {b}{b \left (\frac {d}{d x}y \left (x \right )\right )+a}\right \}, \left \{x =c_{1}+\int \textit {\_}b\left (\textit {\_a} \right )d \textit {\_a} , y \left (x \right )=-\frac {-\textit {\_a} b +\left (c_{1}+\int \textit {\_}b\left (\textit {\_a} \right )d \textit {\_a} \right ) a}{b}\right \}\right ]\right )\right \}\]