The goal of simplifying expressions with third roots is to factor the radicand into a product of two numbers.
One of these two numbers must be a value in which you can take the third root and still get a rational number.
So let's list the factors of 16
Factors:
1, 2, 4, 8, 16
Notice how 8 is the largest value in which you can take the third root and still get a rational number, so lets break 16 down into 8*2