I couldn’t even begin to dream up a program for doing this upgrade. I need to get 3700 items from my zen-cart db to Magento. I don’t care about moving attributes or quantity discounts (qty discounts would be nice) .
You may wish to use Cart2Cart - shopping cart migration service
It supports migrating from Zen Cart to Magento.
Your thousands of items will be moved like a charm with attributes:)
Qty discounts aren’t supported yet.