f(x) = (x² - 3x - 10)(x + 4) becomes (x - 5)(x + 2)(x + 4) when completely factored. Now set each binomial equal to zero.
x - 5 = 0
x = 5
x + 2 = 0
x = - 2
x + 4 = 0
x = - 4
Your zeros are at x = - 4, - 2, and 5. Or at (- 4, 0), (- 2, 0), and (5, 0).