Simplify.
Remove all perfect squares from inside the square root.

Answer:
[tex]2z^{3} \sqrt{14z} [/tex]
Step-by-step explanation:
[tex]\sqrt{56x^{7} } =\sqrt{(14)(2^{2} )(z^{2})(z^{2})(z^{2})(z) } [/tex]
[tex]=2(z)(z)(z)\sqrt{14z} =2z^{3} \sqrt{14z} [/tex]
Hope this helps