\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -{\frac {\sqrt {1- \left ( y \left ( x \right ) \right ) ^{4}}}{\sqrt {-{x}^{4}+1}}}=0} \]
Mathematica: cpu = 0.080010 (sec), leaf count = 14 \[ \left \{\left \{y(x)\to \text {sn}\left (\left .c_1+F\left (\left .\sin ^{-1}(x)\right |-1\right )\right |-1\right )\right \}\right \} \]
Maple: cpu = 0.015 (sec), leaf count = 32 \[ \left \{ \int \!{\frac {1}{\sqrt {-{x}^{4}+1}}}\,{\rm d}x-\int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt {-{{\it \_a}}^{4}+1}}}{d{\it \_a }}+{\it \_C1}=0 \right \} \]
Sage: cpu = 0 (sec), leaf count = 0 \[ \text {Maxima was unable to solve this ODE} \]