We demonstrate that the reduction in width of the ZGNR in such a way suppresses the electron transport which is certainly attributed to the electron scattering at the interface of electrode and scattering region due to electronic structure mismatch between electrode and scattering region. The electron scattering at the interface is further accompanied by spinpolarized Fano-shaped DQI dips which becomes more prominent with the reducing width of ZGNRH. With this, 4ZGNRH in FM state turns out to be a potential candidate for spintronics applications with 50.75 % spin-filtering efficiency. In nutshell, the cooperative effect of destructive QI and spin non-degenerate levels of ZGNR in FM state allows ZGNRH with reduced width to act as efficient spin filters. We believe that these theoretical findings are crucial for the development of new ZGNR-based spintronic devices.