Answer
$3z^{2}\sqrt[4] {z^{3}}$
Work Step by Step
$\sqrt[4] {81z^{11}}$
=$\sqrt[4] {3^{4}\times z^{8}\times z^{3}}$
=$\sqrt[4] {3^{4}}\times \sqrt[4] {z^{8}}\times \sqrt[4] {z^{3}}$
=$3\times z^{2}\times \sqrt[4] {z^{3}}$
=$3z^{2}\sqrt[4] {z^{3}}$
