The effects of excess ZnO addition on phase structure, dielectric and piezoelectric properties in pure and La-doped lead zinc nicobate (PZN)-lead zirconate titanate (PZT) systems have been investigated. Addition of excess ZnO helps suppress and prevents the formation of pyrochlore phase for both systems. However, the effects on electrical properties in the systems were very different, even opposite. For the PZN-PZT system, excess ions possibly exist as second-phase inclusion particles. Based on Raman spectra and the changes in properties, in the La-doped PZN-PZT system, excess ions are very likely to enter A-site lead vacancies. Adding proper excess ZnO in La-like-doped PZN-based systems is an effective approach to achieve a pure perovskite phase, enhanced piezoelectric constant d(33), and reduced dielectric loss.