Answer
$$f_1(x,y,z)=xyz+1.$$
(Other answers are possible.)
Work Step by Step
To get an example of a potential function for the vector $\langle yz,xz,xy \rangle $, we add a constant to the function $f=xyz$. For instance, we can get the function:
$$f_1(x,y,z)=xyz+1.$$
