ZMF (or Zoner Draw document, Zoner Callisto Metafile, etc.) is a family of vector graphics formats associated with Zoner Draw (formerly named Zoner Callisto), a line of graphics software by Zoner, Inc. ZMF probably stands for Zoner Metafile.
Some ZMF files begin with
5c 00 00 00 dd 5a 01 d4 78 56.
Or, some older ZMF formats use a Microsoft Compound File container.