LensForge can not read binary ZMF files. We are working to resolve this.
The LensForge distribution includes lens files in ZMF format from Edmund Optics and ThorLabs. The ZMF file format used by the ZEMAX lens design program is often used as a format for the publication of lens catalogs.
Actually Edmund Optics provides the ZMF file compressed within a self-extracting archive in EXE form intended for Windows computers, but Stuffit Expander for Mac can open it.
To use a ZMF file with LensForge, you just open the file with LensForge and drag the lenses you want into your lens design.