We present high-precision predictions for Z boson-pair production via electron-positron collisions by taking into account a full set of one-loop order scattering amplitudes, i.e., electroweak (EW) corrections together with soft and hard QED radiation. We provide a detailed numerical evaluation, from full EW corrections to pure QED corrections, specifically focusing on the effect of initial beam polarization on the production rate. The left-right asymmetry and angular distributions are also presented. The radiative corrections are largely affected by initial beam polarizations. We get an improvement of around three times with completely polarized beams of e(L)(-) and e(R)(+). We find that the radiative corrections can sizably modify the production rate, typically yielding a total relative correction up to a few tens of a percent. This implies that the full EW corrections are required for e(-)e(+) -> ZZ to match with percent-level accuracy.