We study within an ionic model the static and dynamic structure and the energetics of neutral and charged molecular clusters which have been proposed to exist in liquid ZrC14 and in molten CsC1-ZrC14 mixtures from Raman scattering experiments by G. M. Photiadis and G. N. Papatheodorou (J. Chem. Soc. Dalton Trans. 1998, 981). The model accounts for ionic-shell deformability through (i) effective valences and (ii) electric and overlap polarizabilities, using three disposable parameters which are adjusted to the bond length and to vibrational frequencies of the isolated ZrC14 molecule. The Zr2C18 dimer, which is believed to be present in saturated vapours and in the pure melt, is found in its ground state to consist of two double-cornersharing tetrahedra, yielding a distorted fivefold coordination for the Zr ions at low temperatures. This distortion is essentially averaged out by thermal fluctuations already at room temperature. Chlorination through mixing with CsCI at various compositions favours the ZrC15 anion as well as sixfold, octahedral-like coordinations of the Zr ions in the ZrC16 monomer and in dimers built from face-sharing, edge-sharing or corner-sharing octahedra (Zr2C19, Zr2CII0 and Zr2Cllh respectively). We demonstrate a crucial role of the Cs counterions in stabilizing these complex anions and in determining the energetics of their equilibria.