This study explores sintering and piezoelectricity of ZnO-doped perovskite Pb(In1/2Nb1/2)O-3-Pb(Zn1/3Nb2/3)O-3-PbTiO3 (PIN-PZN-PT) ceramics. The enhanced densification of ZnO-doped PIN-PZN-PT is attributed to the formation of oxygen vacancies by the incorporation of Zn2+ into the perovskite B-site and increased rate of bulk diffusion relative to undoped PIN-PZN-PT. Incorporation of Zn2+ into the perovskite lattice increased the tetragonal character of PIN-PZN-PT as demonstrated by tetragonal peak splitting and increased Curie temperature. Sintering in flowing oxygen reduced the solubility of Zn2+ in the perovskite lattice and resulted in rhombohedral PIN-PZN-PT. Sintering in oxygen prevented secondary phase formation which resulted in a high-piezoelectric coefficient (d(33) - 550 pC/N), high-coercive field (E-c - 13 kV/cm), and high-rhombohedral to tetragonal phase transition temperature (Tr-t - 165 degrees C). We conclude that ZnO-doped PIN-PZN-PT ceramics are excellent candidates for high-power transducer applications.