The only thing you could do is increase the steps per unit by either increasing the microstep setting of the drive if that is possible or increasing the gearing between motor and screw, but that is likely to hit on your rapid speeds.
I dont know what a Zenbot is but unless it is a very rigid and precise machine you will never manage to get that resolution anyway, 0.0001" is a very small size, your tool will probably flex 5 times that

Hood