A new version is out, focussing mainly on reducing the memory footprint required by the interpreter to play games, benefitting all versions: M4ZVM (Release 17) and M3ZVM (Release 7) M1ZVM (Release 7).
All versions have the following improvements:

• Optimized binary size using code rewrite and self-modifying strings
• Reduced file size by moving from zeroed ram to uninitialized
• Used extra memory to increase cache by another 2-3 sectors
• Minor speed improvement including call/return, object and compare
• Bugfix: Some specific error messages were incorrectly generalized
• Bugfix: In a rare edge case, disk full error was not handled properly

The Model 4 64K version (M4ZVM64/CMD) has the following additional improvements:

• Reduced z-stack, combined with size optimization  allowed increase in DynMEM (up from 23 to 24.5k) plus an increase in cache size. This brings two improvements: faster gameplay (less disk I/O) and additional games e.g. Augmented Fourth can now be played
• Bugfix: colour scheme was not properly initialized  which impacted Shogun as the status line was not displayed as inverse

The Model 3 version has the additional benefit:

• The reduced footprint has also reduced the allocated file size, making an additional 1.5k available on the disks.

The Model 1 version similarly has a smaller  disk footprint.