The zeros of a function are the values of x for which y = 0.
The zeros of a function written in the form y = a(x - x₁)(x - x₂) are the numbers x₁ and x₂. This happens because, if we replace x by one of those values, that will zero the value of y:
y(x₁) = a(x₁ - x₁)(x₁ - x₂) = a * 0 * (x₁ - x₂) = 0
y(x₂) = a(x₂ - x₁)(x₂ - x₂) = a * (x₂ - x₁) * 0 = 0
Then, the zeros of the function
Y=-2(x-2)(x-10)
are 2 and 10.