Have been using Mach3 for years with desktop computer and mid sized CNC machine.
Have purchased (not received yet) a Zen Toolworks 12X12 machine with the arduino controller package, have the following questions.

Will Mach4 work with the arduino board?
Will Mach4 run and address the controller from a laptop?
What would I need to accomplish the above?

If I have to stay with Mach3 and a smooth stepper I would have to purchase a Mach3 controllerbox
an additional $300.00 or so, and an additional Mach3 license.

Any help you guys can give me would be appreciated.

Thanks in advance,
jim 

No, you can't use the Arduino controller.
You need a motion controller with a Mach4 plugin.