\[ \boxed { 2\, \left ( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) \right ) y \left ( x \right ) -3\, \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}-4\, \left ( y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.092012 (sec), leaf count = 17 \[ \left \{\left \{y(x)\to c_2 \sec ^2\left (2 c_1+x\right )\right \}\right \} \]
Maple: cpu = 1.638 (sec), leaf count = 37 \[ \left \{ y \left ( x \right ) =4\, \left ( {{\it \_C1}}^{2} \left ( \sin \left ( x \right ) \right ) ^{2}-{{\it \_C2}}^{2} \left ( \sin \left ( x \right ) \right ) ^{2}-2\,{\it \_C1}\,{\it \_C2}\,\sin \left ( x \right ) \cos \left ( x \right ) +{{\it \_C2}}^{2} \right ) ^{-1} \right \} \]