A series of high-temperature solid state chemical reactions was carried out in the quasi-quarternary mixed-halide Cs-Zr-B-(Cl,I) system with stoichiometries aiming for zirconium cluster phases of the Cs-2[(Zr6B)X-15] type (X = mixture of Cl + I). In the phase range from similar to Cs-2[(Zr6B)Cl13I2] to Cs-2[(Zr6B)Cl3I12] the structures of the obtained cluster phases are derived from the orthorhombic CsK[(Zr6B)Cl-15]. At a composition of Cs-2[(Zr6B)Cl-similar to 10 1(similar to 4)] a lower symmetry, monoclinic derivative has been found. X-ray diffraction data of single crystals of three compounds of this phase system were collected, orthorhombic Cs-2[(Zr6B)Cl12.99(3)I2.01] (1), (Pmma, Z = 4, a = 19.304(4), b = 14.617(3), c = 9.921(2) angstrom, R1/wR2 = 0.0444/0.0886), monoclinic Cs-2[(Zr6B)Cl10.63(3)I4.37] (2), (P2/c, Z = 4, a = 14.9502(3), b = 10.0098(2), c = 19.8798(4) angstrom, beta = 90.977(1) R1/wR2 = 0.0460/0.1182), and orthorhombic Cs-2[(Zr6B)-Cl8.79(4)I6.21] (3) (Pmma, Z = 4, a = 20.0534(4), b = 15.1488(3), c = 10.1739(2) angstrom, R1/wR2 = 0.0494/0.1123). These compounds are obtained as single phase products. As in other known mixed-halide systems halide ordering is observed, such that the different halide sites have different amounts of Cl and I. With increasing amount of iodide, relative to Cl, the cluster-interconnecting halide sites are more and more occupied by I. For the first time it is observed for 3 that a halide site, which forms a linear bridge between two neighboring Zr6B cluster units (so far known examples are solely occupied by Cl), is statistically mixed occupied by Cl and 1. Nevertheless, both halide types achieve acceptable bonding situations (bond lengths) because the I atoms are moved out of the linearly bridging position, thereby achieving longer Zr-X distances than the Cl atom, which remains linearly bridging. The generally interesting aspect of this paper is that in the very complex systems the atoms of the mixed occupied sites as well as those of the cation sites arrange with respect to the atomic environment, such that all of them have optimized bonding situations.