We demonstrate the generation of enhanced tuneable harmonics of the mid-infrared (1250 -1400 nm), 65 fs pulses in laser-produced zinc plasma in the regions of Zn II and Z III autoionizing states (77 and 68 nm, respectively). The role of singly and doubly ionized zinc in the modification of harmonic spectra was analyzed by variation of plasma formation conditions. Microprocesses and the propagation effect are also discussed to describe the narrowing of enhanced emission spectra.