Simplify the radical expression. Find the missing expression.

$\displaystyle\sqrt{{{108}{{x}}^{{11}}{{y}}^{{4}}{{z}}^{{9}}}}={6}{\left|{{x}}^{{5}}\right|}{{y}}^{{2}}{{z}}^{{4}}\sqrt{{?}}\usepackage{cmbright}\Huge\$

The missing expression is _____.