\[ y(x) \left (a+x^2+y(x)^2\right ) y'(x)+x \left (-a+x^2+y(x)^2\right )=0 \] ✓ Mathematica : cpu = 0.270129 (sec), leaf count = 149
\[\left \{\left \{y(x)\to -\sqrt {-\sqrt {a^2+4 a x^2+4 c_1}-a-x^2}\right \},\left \{y(x)\to \sqrt {-\sqrt {a^2+4 a x^2+4 c_1}-a-x^2}\right \},\left \{y(x)\to -\sqrt {\sqrt {a^2+4 a x^2+4 c_1}-a-x^2}\right \},\left \{y(x)\to \sqrt {\sqrt {a^2+4 a x^2+4 c_1}-a-x^2}\right \}\right \}\] ✓ Maple : cpu = 0.052 (sec), leaf count = 125
\[\left \{y \left (x \right ) = \sqrt {-x^{2}-a -\sqrt {4 a \,x^{2}+a^{2}-4 c_{1}}}, y \left (x \right ) = \sqrt {-x^{2}-a +\sqrt {4 a \,x^{2}+a^{2}-4 c_{1}}}, y \left (x \right ) = -\sqrt {-x^{2}-a -\sqrt {4 a \,x^{2}+a^{2}-4 c_{1}}}, y \left (x \right ) = -\sqrt {-x^{2}-a +\sqrt {4 a \,x^{2}+a^{2}-4 c_{1}}}\right \}\]