For the FeI atoms, we see 3 axes with a 4 fold rotational symmetry. Therefore the EFG will vanish at the site of a FeI atom.
For the FeI atoms we find one 4 fold axis (the axis through the N atoms) and 2 axes with 2 fold rotational symmetry. Therfore the 4 fold axis is the z-axis of a PAS for which eta is 0 so axially symmetric around this axis.