Simplify. Multiply and remove all perfect squares from inside the square roots. Assume zzz is positive.

Step-by-step explanation:

Put the square roots together

4*5 * sqrt(14z^2 * 21z^3)

4*5 * sqrt(2*7 * z^2 * 3*7 z^2 * z)

The rule is to remove the perfect square from under the square root sign, you take 1 member of the perfect square out of the root sign, and throw the other one away. If there are an odd number of factors under the root sign, leave one of them alone.

4*5 * 7 z * z sqrt(2 * 3 * z)

140 z^2 * sqrt(6z)