Final answer:
The flux through the square in the xy-plane at z = 0 is zero.
Step-by-step explanation:
To find the flux for this field through a square in the xy-plane at z = 0, we need to first determine the electric field passing through the square. Since the field is directed along the z-axis, it is perpendicular to the xy-plane. Therefore, the flux through the square will be zero.