\[ y'(x)=\frac {x^2 \sqrt {4 a x-y(x)^2}+2 a}{y(x)} \] ✓ Mathematica : cpu = 2.17623 (sec), leaf count = 103
\[\left \{\left \{y(x)\to -\frac {\sqrt {4096 a^6 x \left (36 a-x^5\right )+128 a^3 e^{c_1} x^3-e^{2 c_1}}}{192 a^3}\right \},\left \{y(x)\to \frac {\sqrt {4096 a^6 x \left (36 a-x^5\right )+128 a^3 e^{c_1} x^3-e^{2 c_1}}}{192 a^3}\right \}\right \}\]
✓ Maple : cpu = 0.182 (sec), leaf count = 27
\[ \left \{ -\sqrt {- \left ( y \left ( x \right ) \right ) ^{2}+4\,ax}-{\frac {{x}^{3}}{3}}-{\it \_C1}=0 \right \} \]