Glasses with nominal molar compositions xZnO-(67-x)SnO-33P2O5 were prepared and their thermal and optical properties are reported. Density, glass transition temperature, thermal expansion coefficient, viscosity, and refractive index change systematically when ZnO replaces SnO. Raman and infrared spectroscopies provide information about the phosphate anions that constitute the glass network. The compositional trends in glass properties are explained considering the linkages between Sn- and Zn-polyhedra and these different phosphate anions. Property trends fall into three compositional ranges defined by low ZnO concentration (0 ≤ x ≤ 20, region I), intermediate ZnO concentration (20 < x ≤ 40, II), and large ZnO concentrations (40 < x ≤ 50, III).