I would love to see the two uc_coupon modules merging eventually. However, for now I've found that that zmove's version ("Improved Coupon Discount") works better for my online store. I tested both versions, but discovered that I needed the features added by zmove's enhancements to the original version.
Is there any chance of getting the fix for working with uc_taxes patched into zmove's version of this module? I see that you were involved in finding the proper fix for that bug and correcting it in the "original" version. (http://drupal.org/node/350359#comment-1222168)
If you don't want to patch zmove's module, maybe you could just give some pointers so that I can successfully patch my own copy of zmove's "Improved" version of the module.