Answer:
2, -2 and 1/2
Explanation:
As the the first coefficient is 2 and the last number is 4 1/2, 2, -2 seem likely zeros ( By the rational roots theorem).
f(2) = 2*8 - 4 -16 + 4 = 0 so 2 is a zero.
f(-2) = -16 - 4 +16 + 4 = 0 so -2 is a zero
f(1/2) = 2*1/8 - 1/4 - 4 + 4 = 0 so 1/2 is the other zero.
Since the highest degree is 3 the maximum number of zeroes is 3.