FeI: In this case we see that FeI has 3 four-fold rotational axes. We can choose any one of them to be the z-axis in PAS, which will result in η=0, and thus axial symmetry. Furthermore, EFG will be zero, because we have more than 2 four-fold symmetry.

FeII: In this case, we have 1 four-fold rotational axis, and 2 two-fold rotational axes. The four-fold axis can be chosen to be the z-axis in PAS with η=0. We cannot say wheter or not EFG will be zero.