Fe-1: it has 3 four-fold axes, thus resulting in a zero EFG-tensor.
Fe-2: If we treat 2a and 2b differently, it has 3 two-fold axes and thus a non-zero EFG-tensor.
If we treat 2a and 2b the same, we have 2 two-fold axes and 1 four-fold axes and thus a zero EFG-tensor