ZMM 2011.12.18 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. This program was originally developed by ZMM Software Inc. The most popular versions among the program users are 2011.12.18 and 2010.07.28. We recommend checking the downloaded files with any free antivirus. The software is categorized as Education Tools.
From the developer:
ZMM is a molecular modeling program for theoretical studies of systems of any complexity: small molecules, peptides, proteins, nucleic acids, and ligand-receptor complexes.
ZMM searches optimal structures in the space of generalized coordinates: torsion angles, bond angles, bond lengths, positions free molecules and ions, and orientation of free molecules. Any generalized coordinate may be kept fixed.
You may want to check out more software, such as Maxima and Minima, DAC Express or IUCLID5, which might be similar to ZMM.