Can I hook up the Glas WiFi Thermostat with oil furnace in basement and central ac in attic
Looking at the installation instructions found here, I see two important details.  First, the thermostat does have a connection for Rc and Rh.  When you have two thermostats and two systems located in different areas, you normally have two low voltage transformers for the control systems.  The red wire from the heat goes to Rh, and the red wire from cooling goes to Rc.

The other subtle but important bit is this note:


  Note: If you have only one R wire, connect to RC. 


This tells us that Rc is the "main" red wire connection, and the common wire (that is required) must also come from the cooling system.

So, yes, this thermostat should work, but when it comes to hooking up a C wire, that will need to come from the cooling system.  If your heating and cooling system have separate fans (blowers), then you might need to wire the furnace so that the fan always comes on with the heat and you will not have separate heat fan control.

Check the manual for other details and even call their customer support because I don't have all the facts, but it at least seems it's worth a try or more research.