\[ \boxed { \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}\sin \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) -y \left ( x \right ) =0} \]
Mathematica: cpu = 0.036505 (sec), leaf count = 28 \[ \text {Solve}\left [\left \{x=c_1+\text {K$\$$1487319} \sin (\text {K$\$$1487319})-\cos (\text {K$\$$1487319}),y(x)=\text {K$\$$1487319}^2 \sin (\text {K$\$$1487319})\right \},\{y(x),\text {K$\$$1487319}\}\right ] \]
Maple: cpu = 0.047 (sec), leaf count = 32 \[ \left \{ x-\int ^{y \left ( x \right ) }\! \left ( {\it RootOf} \left ( \sin \left ( {\it \_Z} \right ) {{\it \_Z}}^{2}-{\it \_a} \right ) \right ) ^{-1}{d{\it \_a}}-{\it \_C1}=0,y \left ( x \right ) =0 \right \} \]