Hi,
interesting looking machine.
I don't think that Mach4 can run two Gcode files simultaneously and I am fairly certain it can only run one motion controller at a time.
One possibility I could forsee would require two separate Mach4 machines, each on its own PC with its own motion controller, and having
synchronizing signals pass back and forth between them.
Clearly the way Mach is written it is meant to run multiple instances, in which case you could have one PC run two machines. You would have
to ask NFS about that, while it looks as if multiple instances are the intention it may not yet be a reality.
Craig