Our inventory ships from multiple locations. The location it ships from is determined during order processing as the closest to the user which has positive supply for the item.
If you have multiple ship from locations you aren't required to provide a zip code in your listing, and you shouldn't be being penalized for this.
The problem is, we manage our inventory via the API, which states that in order to publish an offer a single inventory location must be chosen. This is very problematic, especially if it leads the user and/or ebay to think that we're misleading them in our listing.
I would greatly appreciate any guidance we can get on this.