\[ \left (x^4+y(x)^2\right ) y'(x)-4 x^3 y(x)=0 \] ✓ Mathematica : cpu = 0.109119 (sec), leaf count = 53
\[\left \{\left \{y(x)\to \frac {1}{2} \left (c_1-\sqrt {4 x^4+c_1{}^2}\right )\right \},\left \{y(x)\to \frac {1}{2} \left (\sqrt {4 x^4+c_1{}^2}+c_1\right )\right \}\right \}\] ✓ Maple : cpu = 0.278 (sec), leaf count = 41
\[ \left \{ y \left ( x \right ) =-{\frac {1}{2}\sqrt {4\,{x}^{4}+{{\it \_C1}}^{2}}}+{\frac {{\it \_C1}}{2}},y \left ( x \right ) ={\frac {1}{2}\sqrt {4\,{x}^{4}+{{\it \_C1}}^{2}}}+{\frac {{\it \_C1}}{2}} \right \} \]