Shipping costs with Printify

[ChugnMugs]

Hello, I hope this finds you well!

I want to include shipping cost in my product cost, and then advertise the product with "Free Shipping!" for domestic shipments. Of note, I am using Printify, and don't want the additional domestic shipping costs added upon order fulfillment; cant this be done? 

Additionally, when using Printify, do I need to set up shipping zones? Or are shipping costs shown(as provided through the Printify integration) to the customers when they are checking out?

Basically, I don't want my customer's to get charged for shipping twice.