A high Figure of merit (FOM) is expected to justify the role of any TCO material as Transparent conducting electrode in the state-of-the-art devices. Here, we are reporting the superior value of Haacke’s FOM of the order of 0.4 × 10⁻³ Ω⁻¹ for Fe-doped ZTO nanostructured films. Optical properties reveal higher optical transparency of 86% (x = 0.08) along with band gap curtailing by about 0.3 eV for Fe-doped samples. Electrical measurements give high carrier concentration (10²⁰ cm⁻³) and low resistivity (10⁻³ Ω cm) along with improved mobility that demonstrate electron-cloaking effect at highest dopant concentrations. A significant broadening of the T_2g Raman characteristic mode indicates increased degeneracy along with phonon confinement effect. The valence band spectra reveal an upshift in VBM and CBM with Valence band offset value varying from 3.08 to 1.98 eV. Time domain terahertz measurements reveal an appreciable decrease in absorption coefficient (4000 cm⁻¹ to 5 cm⁻¹ at 0.7 THz) and the refractive index dispersion change to nearly constant value of 1.8 between 0.8 and 2.5 THz with Fe doping in ZTO films. These results are very important for the development of transparent electronics and active materials for the components for manipulating THz spectrum.