I just found a new, new to me, interface for running the ZTW machines from a USB port. It's called UC100 and the information can be found here:
http://cncdrive.com/UC100.html The one I have came with a USB cable, a db25 connector and a gender changer. The USB cable is plugged into the computer and the other end is plugged into the db25 connector. The gender changer is plugged into the db25 connector, and that is plugged into your controller. Load the driver from the site listed above and there you go. I am running Mach 3 and needed to choose the UC100 when the program first starts and so far everything works just as if you had a printer port plugged in. Now I'm not tied to the old boat anchor computer which relies on the printer port to use my ZTW 12x12.
HINT: Maybe ZTW will carry this as an added feature to this great line of machines. What do you think Xin??