I recently integrated a Xero account with over 15,000 invoices from Trade Gecko. Eventually we will move them to Zoho Inventory.
The client needed rich reporting based on approx 300 products. The challenge was Xero had 100,000 products, as Trade Gecko allowed them to change their product names, SKU's were not unique (historical issue) etc.
As you can image it was a migration challenge. We couldn't use an off the shelf API, as they would have created many duplication issues from Clients to Products.
We had to build a custom API that considered all the mapping scenarios, with 4 random products to capture the anomalies based on key words in the Xero Product description.
So 15,000 invoices successfully migrated with over 100,000 products correctly mapped to the unique 300 products in Zoho. Which means we now have powerful reports.
If you're experiencing a Xero API / Data migration issue please touch base. We have not made this an Public API but would be interested to know if there is a market demand for it.