Answer
4xy, -4xy
Work Step by Step
$\sqrt[4] {(4xy)^4}$
$\sqrt[4] {(4xy)^4} = ((4xy)^4)^{1/4}$
$((4xy)^4)^{1/4} = ((4xy)^{4/4}$
$(4xy)^{(4/4)} = (4xy)^1$
$(4xy)^1=4xy$
Because the root and power have a product of one, we have to also consider the negative value of the answer we found.