Category-Specific Free Shipping Limitations

We have a customer with some very specific shipping needs, and are hoping that this forum post will help us get some guidance on how we can implement some modifications to fit their needs.

The main requirement was that they wanted to offer free shipping on orders over $100 in a single category. We currently have modifications in place to meet this requirement, however we need to impose several limitations, specifically:

1. We want the free shipping only to be offered to customers within the 48 US states.
2. We want the only method available for the free shipping to be regular UPS Ground.

One other shipping-related issue (not related to the above) that we need to address is that we would like to have USPS be a shipping option available to international customers. Currently, only UPS methods are available. At one time in the past, apparently USPS was available for international customers, and it is activated as a shipping method.

In advance, we most sincerely appreciate any advice and assistance!

You should sign up for the News & Announcement forum:
http://www.zen-cart.com/forumdisplay.php?2-Zen-Cart-Release-Announcements

then read the update for the USPS March 7, 2014 K3 release and ensure that you have that installed:
http://www.zen-cart.com/showthread.php?212467-USPS-RateV4-Intl-RateV2-Mar-7-2014-Version-K3-%28First-Class-changes%29

Is the 1 Category based on the master_categories_id or the parent_id with all subcategories included to check the $100.00?

You could use the Free Shipping Options freeoptions you could build a Zone Definitions with the DETAILS defined for who should by offered Free Shipping on Total >= 100.00 and customize it to check the total on just the one Category of Products ... or you would need to customize the UPS shipping module to change Ground to 0.00 when the Category is >= 100.00 and the right Zone is being used on the shipping address (this is harder to do, but could be done) ...

Also, what happens on a Mixed Cart of Products from the Category for Free Shipping via UPS ground if >= 100.00 and Products from other Categories?

Does this need to some how calculate the shipping and exclude the the Category for Free Shipping from the calculation? And is the shipping cost for those Free Shipping Products only done on the UPS ground? If so, this could get very, very complicated ...