ZenCart Version: 4.4.9 for now.

Can someone line me out on the process of QuickBooks integration?

I know there's something called QBI (QuickBooks Integration). Is that a QuickBooks program, a third party thing, or a ZenCart module?

Where do you get it?

How difficult is it to integrate into ZenCart?

Any hassles or common bugs with it?

Thank you very much.