The value of ${\left({\left({\log }_{2}9\right)}^2\right)}^{\frac{1}{{\log }_2\left({\log }_{2}9\right)}}\times {\left(\sqrt{7}\right)}^{\frac{1}{{\log }_{4}7}}$is 

    ${\log }_2{9}^{\frac{2}{{\log }_2\left({\log }_{2}9\right)}}\times 7^{\frac{1/2}{{\log }_{4}7}}={\left(\log {}_{2}9\right)}^{\frac{2 \log {}_{2}2}{\log {}_2\left(\log {}_{2}9\right)}} 7^{\frac{1}{2}\log {}_{7}4}={\left({\log }_{2}9\right)}^{2{\log }_{{\log }_{2}9}^2}\times 7^{{\log }_7{4}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}}=4\times 2=8$     $\left( \sin ce a^{\log {}_{a}x}=x\right)$