(x + y + z) = 0 అయితే \(\frac{{{{\rm{x}}^2}{\rm{\;}} + {\rm{\;}}{{\rm{y}}^2} - {\rm{\;}}{{\rm{z}}^2}}}{{{{({\rm{x\;}} + {\rm{\;y}})}^{2{\rm{\;}}}} - {\rm{\;}}{{\left( {{\rm{x\;}} - {\rm{\;y}}} \right)}^2}{\rm{\;}}}}\) విలువను కనుగొనండి