Question about finding a component of the electric field

Let's say I have the electric potential as a function of x, y, and z: V(x,y,z)

Now I want to find the x component of the electric field along the x-axis: E_x(x,0,0)


I could take the derivative of the potential wrt x and then plug in zero for y and z.

However if I was to plug in zero for y and z in the potential function, and then derive, would that be valid?