\[ -x \sqrt {\left (y(x)^2-4 x^2\right ) \left (y(x)^2-x^2\right )}+x y'(x)-y(x)=0 \] ✓ Mathematica : cpu = 0.593427 (sec), leaf count = 143
\[\text {Solve}\left [\frac {2 \left (\frac {y(x)}{x}-2\right )^{3/2} \sqrt {-\frac {4}{\frac {y(x)}{x}-2}-1} \sqrt {-\frac {3}{\frac {y(x)}{x}-2}-1} \sqrt {\frac {1}{\frac {y(x)}{x}-2}+1} F\left (\left .\sin ^{-1}\left (\frac {\sqrt {-1-\frac {3}{\frac {y(x)}{x}-2}}}{\sqrt {2}}\right )\right |-8\right )}{\sqrt {\frac {y(x)}{x}-1} \sqrt {\frac {y(x)}{x}+1} \sqrt {\frac {y(x)}{x}+2}}=c_1+\frac {x^2}{2},y(x)\right ]\] ✓ Maple : cpu = 0.352 (sec), leaf count = 86
\[ \left \{ \int _{{\it \_b}}^{x}\!{1 \left ( {\it \_a}\,\sqrt {4\,{{\it \_a}}^{4}-5\,{{\it \_a}}^{2} \left ( y \left ( x \right ) \right ) ^{2}+ \left ( y \left ( x \right ) \right ) ^{4}}+y \left ( x \right ) \right ) {\frac {1}{\sqrt {4\,{{\it \_a}}^{4}-5\,{{\it \_a}}^{2} \left ( y \left ( x \right ) \right ) ^{2}+ \left ( y \left ( x \right ) \right ) ^{4}}}}}\,{\rm d}{\it \_a}+\int ^{y \left ( x \right ) }\!-{{\it \_b}{\frac {1}{\sqrt {4\,{{\it \_b}}^{4}-5\,{{\it \_b}}^{2}{{\it \_f}}^{2}+{{\it \_f}}^{4}}}}}{d{\it \_f}}+{\it \_C1}=0 \right \} \]