\[ y''(x)+y(x)^3 y'(x)-y(x) y'(x) \sqrt {4 y'(x)+y(x)^4}=0 \] ✓ Mathematica : cpu = 0.30164 (sec), leaf count = 33
DSolve[y[x]^3*Derivative[1][y][x] - y[x]*Derivative[1][y][x]*Sqrt[y[x]^4 + 4*Derivative[1][y][x]] + Derivative[2][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to \sqrt {2} e^{c_1} \tan \left (2 \sqrt {2} e^{3 c_1} (x+c_2)\right )\right \}\right \}\] ✓ Maple : cpu = 0.316 (sec), leaf count = 35
dsolve(diff(diff(y(x),x),x)+y(x)^3*diff(y(x),x)-y(x)*diff(y(x),x)*(y(x)^4+4*diff(y(x),x))^(1/2)=0,y(x))
\[y \left (x \right ) = \frac {\tan \left (\left (\frac {1}{c_{1}^{2}}\right )^{\frac {3}{2}} \left (c_{2}+x \right )\right )}{c_{1}}\]