\[
\boxed{
{\it d4y} \left( x \right)  \left( \sin \left( x \right)  \right) ^{4}+2\, \left( {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right)  \right)  \left( \sin \left( x \right)  \right) ^{3}\cos \left( x \right) + \left( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right)  \right)  \left( \sin \left( x \right)  \right) ^{2} \left(  \left( \sin \left( x \right)  \right) ^{2}-3 \right) + \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) \sin \left( x \right) \cos \left( x \right)  \left( 2\, \left( \sin \left( x \right)  \right) ^{2}+3 \right) + \left( {a}^{4} \left( \sin \left( x \right)  \right) ^{4}-3 \right) y \left( x \right) =0}
\]