\[ y'(x)=\frac {1}{2} x \left (2 \sqrt {x^3-6 y(x)}+x\right ) \] ✓ Mathematica : cpu = 0.190465 (sec), leaf count = 33
DSolve[Derivative[1][y][x] == (x*(x + 2*Sqrt[x^3 - 6*y[x]]))/2,y[x],x]
\[\left \{\left \{y(x)\to \frac {1}{24} \left (-9 x^4+4 x^3+36 c_1 x^2-36 c_1{}^2\right )\right \}\right \}\] ✓ Maple : cpu = 0.325 (sec), leaf count = 22
dsolve(diff(y(x),x) = 1/2*x*(x+2*(x^3-6*y(x))^(1/2)),y(x))
\[c_{1}-\frac {3 x^{2}}{2}-\sqrt {x^{3}-6 y \left (x \right )} = 0\]