Tracking SalesIQ Across Multiple Domains

Tracking SalesIQ Across Multiple Domains

I use Unbounce for my Landing Pages and Wordpress for my website to display our product.

Our unbounce domain uses a sub domain, and one of the shorter URLs we own.  It may look something like this:   http://try.example.com

Our webiste domain would be:   http://exampledomainlong.com

SalesIQ visitor tracking code has been placed on both platforms. 

Are there issues with tracking across domains?

What links ZCRM and SalesIQ so that data is communicated between these platforms?  A cookie or IP Address?  

Thank you.