Hi,
I have more than 5 years experience in Zencart. I have developed alot Zencart Shipping modules.
I can help you to develop this new shipping module, its easy to install and config via zencart admin, module will get products in customer shopping cart, then find shipping rates in Spreadsheet file, then show shipping price at checkout page .
I can start and finish this module in the next 2-3 days.
Thanks