Do I need one 12 zone system or two 6 zone systems?

I'm planning to purchase a Konnected Alarm Panel to replace the brains of my old DSC wired system.

I have a three story house including a basement in-law apartment.  The alarm system can be set independently for the in-law apartment and the rest of the house.  There are two boards for the DSC system, one on the top floor and one in the basement.  They are connected to each other with what appears to be a 4 conductor phone line (RJ11 style).

It is not feasible for me to reroute all of the wires from the basement to the top floor, so I'm looking at installing one Konnected panel on the top floor and one in the basement.

For that setup, do I need to purchase one 12 zone system or two 6 zone systems?  If I need to purchase two 6 zone systems, can I use a single SmartThing Hub to control both of them?