The (supposed - I say this because they are not the most recent and I don’t expect Amazon is going to fix that) current XSD’s are found here: https://sellercentral.amazon.com/help/hub/reference/1611?ie=UTF8
However, over a year ago I received an email from Amazon with this in it (I never got another email on this):
As previously announced on May 11, 2021, Amazon is launching new Product Types across XSDs worldwide. The goal is to enable enhanced product search and a simplified product overview by surfacing key product information in a structured format at the top of product detail pages instead of unstructured bullet points. This will help customers to read through the top product specifications, evaluate key differences between products and make purchase decisions quicker.
This first phase of 120 new Product Types are available as of July 14, 2021. You can download the list of affected Product Types (link removed but see ** Below) with the corresponding XSD categories in Microsoft Excel format (.xlsx).
For each new Product Type, you can view the XSD by clicking the link in the Microsoft Excel list.
**If you want to PM me I’ll give you the excel doc that is downloaded with the links to many new XSD’s. I’m not sure I should post the link in the forums. I think it would be OK, but just in case.