In order to simplify this expression, this is how to do it.
I assume that the expression is like this one:
sqrt (27x^4 / 75y^2)
so
sqrt ( 9*3 x^4 / 25*5y^2)
= (3x2 / 5y ) * sqrt(3 / 5)
So, the final expression or the simpler expression based from the given question is (3x2 / 5y ) * sqrt(3 / 5)