Fe1-atom:
We see 3 4-fold rotation axes. Due to the first theorem one of these axes (x, y, z) can be chosen as the z-axis of the PAS, with eta 0. From the second theorem, we get that the EFG tensor is 0.
At Fe2-atom, we see a 4-fold rotation axis and 2 2-fold rotational axes so these can also be chosen as the z-axis of the PAS.