Partial Derivatives & the Gradient · Medium problem

Near certain points, the equation $x^{2} + yz - xz = 8$ defines $z$ implicitly as a function of $x$ and $y$. On the cross-section $y = 3$, there are two points where $\dfrac{\partial z}{\partial x} = 0$. Find $z$ at the one with the smaller $x$.