\[ y(x) \left (a+x^2+y(x)^2\right ) y'(x)+x \left (-a+x^2+y(x)^2\right )=0 \] ✓ Mathematica : cpu = 0.21603 (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 = 0.032 (sec), leaf count = 125
\[ \left \{ y \left ( x \right ) =\sqrt {-{x}^{2}-a-\sqrt {4\,a{x}^{2}+{a}^{2}-4\,{\it \_C1}}},y \left ( x \right ) =\sqrt {-{x}^{2}-a+\sqrt {4\,a{x}^{2}+{a}^{2}-4\,{\it \_C1}}},y \left ( x \right ) =-\sqrt {-{x}^{2}-a-\sqrt {4\,a{x}^{2}+{a}^{2}-4\,{\it \_C1}}},y \left ( x \right ) =-\sqrt {-{x}^{2}-a+\sqrt {4\,a{x}^{2}+{a}^{2}-4\,{\it \_C1}}} \right \} \]