With zeros of 4, -2, and 2, your respective factors will be (x - 4)(x + 2)(x - 2).
Since there is a leading coefficient of -3, the complete factor form is:
-3(x - 4)(x + 2)(x - 2)
To find the expanded form, multiply the factors and combine like terms:
-3(x - 4)(x2 + 2x - 2x - 4)
-3(x - 4)(x2 - 4)
-3(x3 - 4x2 - 4x + 16)
-3x3 + 12x2 + 12x - 48