One other thing that I need to add that probably makes a big difference as far as legalities go is the item is simple clothing and accessories, name brand stuff, nothing hazardous or exclusive.
Hopefully XYZ company and you have a license or permission to export and import. The flow of payments is equally important. There are SIC codes for each item. The local export office run by DOC is your best place to get started. They are generally very helpful. Check them out.
From what you have described there are two issues 1) Customs duty (tax) in ABC country - it all depends on the terms of sale that you and your buyer (XYZ) agreed. If you agreed with the buyers that you will take the responsibility to clear Customs in country ABC, then you have to figure out what the process for clearing goods in ABC country is, in almost all countries including the U.S. paying duty is only one step in what sometimes can be a complicated process. 2) Income and business taxes in the U.S.- that you have to get advice from a tax expert.. For both issues, I suggest that you speak to qualified experts so that it will not be a bad experience.
If you have a business that is based in the USA and you work with a partner similar to Amazon in another country are there any considerations you need to worry about other than taxes and customs?
For example, you live in the USA, you buy merchandise here and mail it to company XYZ based in country ABC, company XYZ lists the items on their website in country ABC, the customers go to the website and buys the item and pays company XYZ directly, company XYZ packs up the item and ships it to the customer. Company XYZ pays you the money for the item minus their commision and listing fee's.
Is there anything special you need to do other than paying customs taxes in country ABC and nomral income and business taxes in the USA?