x = 5
x = 4
x = 2
Basically to find the zeros (which just means that f(x) = 0) you can just take any one of those terms in parentheses and figure out what X needs to be to make the term zero.
(x-5) = 0 would mean that x = 5
(x-4) = 0 would means that x = 4
(x-2) = 0 would mean that x = 2
If any one of those terms in parentheses = 0, the whole equation is zero (anything x 0 = 0) so those are your zeroes of the function