The following was posted in a previous thread:

The imaging path is located in a compiled file called IMG, which is
located inside the LINUX3.TAR file, which is inside the LINUX3.TGZ on the
Zen imaging boot CD. IMG can be opened with a hex editor, then
the /path/images/ string can be replaced with a string of your choice.
Here are the steps I used:
Full Article:

These files do not appear to exist in version and instead there
appears to be a file called initrd. Extracting the contents of this file
does not reveal any reference to an img file. This may not be supported
but I sure would like to be able to modify the /path/archive.zmg from the
default. Anyone have new info on how to do this?