The first quaternary bismuthide Zintl phase Ba8Zn2-xIn3+xBi10 (exp.: 0.21 ≤ x ≤ 0.47) was obtained by reacting the corresponding elements at high temperature. Its crystal structure consists of linear intergrowth of two distinct polyanionic blocks, combining the most typical features of ternary alkali-earth pnictide Zintl phases with group 12 and group 13. Hence, MBi4 tetrahedra (M = Zn or In) are the basic building units. However, the clear difference in the condensation mode of the MBi4 tetrahedra when centered by either the transition metal Zn (edges sharing) or the main group metal In (corners sharing) ascribes the quaternary phase with enhanced structural complexity when compared to the respective ternary systems with only group 12 or group 13 element. The coordination site preference between divalent Zn and trivalent In atoms is also in agreement with maximizing the stability of the system, and it may provide a unique approach to rationally explore structurally complex quaternary pnictide Zintl phases. The title compound is predicted to be charge balanced Zintl phase for x = 0, and the refined values between x = 0.21 and 0.47 suggest substantial electronic flexibility that is crucial to fine tune the compound transport properties by doping using appropriated iso-or alio-valent chemical substitutions. These findings agreed with the computational studies as the theoretical band structures obtained from DFT calculations, predicted the title compound to be heavily doped (n-doped) semiconductor with a narrow band gap. In addition, total energy calculation could also confirm the coordination site preference between Zn and In as thermodynamically driven. Efforts to produce phase pure samples for the investigation of their thermoelectric properties are particularly warranted. Artwork (for TOC only) "Ba 3 ZnInBi 4 " + "Ba 5 ZnIn 2 Bi 6 "