Cobalt-doped dicalcium zinc germanate, synthesized by slow cooling from the melt, is monoclinic and has a layered structure, which is different from the modulated melilite-type structure of Ca(2)ZnGe(2)O(7). The monoclinic form has two different Ca, one Zn and two Ge sites, and seven independent O-atom positions; all are in general position 4e of the space group P2(1)/n. The topology of the structure is described and compared with that of Ca(2)ZnGe(1.25)Si(0.75)O(7).