The number of Zintl phases containing polyhedral clusters of tetrel elements that are accessible for chemical reactions of the main-group element clusters is rather limited. The synthesis and structural characterization of two novel ternary intermetallic phases A(14)ZnGe(16) (A = K, Rb) are presented, and their chemical reactivity is investigated. The compounds can be rationalized as Zintl phases with 14 alkali metal cations A(+) (A = K, Rb), two tetrahedral [Ge-4](4-) Zintl anions, and one anionic heterometallic [(Ge-4)Zn(Ge-4)](6-) cluster per formula unit. The Zn-Ge cluster comprises two (Ge4) tetrahedra which are linked by a Zn atom, with one (Ge-4) tetrahedron coordinating with a triangular face (eta(3)) and the other one with an edge (eta(2)). [(eta(3)-Ge-4)Zn(eta(2)-Ge-4)](6-) is a new isomer of the [(Ge-4)Zn(Ge-4)](6-) anion in Cs6ZnGe8. The phases dissolve in liquid ammonia and thus represent rare examples of soluble Zintl compounds with deltahedral units of group 14 element atoms. Compounds with tetrahedral [E-4](4-) species have previously been isolated from solution for E = Si, Sn, and Pb, and the current investigation provides the "missing link" for E = Ge. Reaction of an ammonia solution of K14ZnGe16 with MesCu (Mes = 2,4,6-(CH3)(3)C6H2) in the presence of -crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) yielded crystals of the salt [K(-crown-6)](2)K-2[(MesCu)(2)Ge-4](NH3)(7.5) with the polyanion [(MesCu)(2)Ge-4](4-). This MesCu-stabilized tetrahedral [Ge-4](4-) cluster also completes the series of [(MesCu)(2)Si4-xGex](4-) clusters, which have previously been isolated from solution for x = 0 and 0.7, as the end member with x = 4. The electronic structures of [(Ge-4)Zn(Ge-4)](6-) and [(MesCu)(2)Ge-4](4-) were investigated in terms of a molecular orbital description and analyses of the electron localization functions. The results are compared with band structure calculations for the A(14)ZnGe(16) phases (A = K, Rb).