Given the function $f_{a}(x) = x^{5} - 5ax + a$, defined on the set of real numbers, determine for which values of the parameter $a > 0$ the function has three distinct real zeros.
Given the function $f_{a}(x) = x^{5} - 5ax + a$, defined on the set of real numbers, determine for which values of the parameter $a > 0$ the function has three distinct real zeros.