> Is it possible for ZipMax to compress in other formats besides Zip format?

No. Zipmax was created to optimize zip (and only) zip compressed archives. Zipmax does a lot low-level zipstructure modifying (copying compressed file data, etc.) which will only work with zip.

Theoretically you can do that with other formats, too. But a) you have to know the structures and b) some formats aren't free to use