Brainstorming solutions to add AC to a home with two separated, ducted furnaces

Hi! I just moved into a home that has two 44,000 BTU natural gas furnaces installed in the crawl space and the attic. Each of these furnaces pushes hot air into the home through ducts upstairs and downstairs, but they are completely separated systems. Two thermostats. Two sets of ducts. Two furnaces. As the summer starts to kick off here in Oakland, CA, I'm trying to put my brain toward adding a single condenser to the home with simple refrigerant lines going to two different evap coils in the attic and the crawl space to pump cool air through the same ducts. It seems like a logically simple question, but everything I try to search for has me reading about ductless mini-splits to no end. I want a multi-zone, ducted, air conditioner, I think, but I honestly don't know and I'm having a hard time explaining this to contractors.

Thanks for having me here! I hope my question is clear!

source https://hvac-talk.com/vbb/threads/2228295-Brainstorming-solutions-to-add-AC-to-a-home-with-two-separated-ducted-furnaces?goto=newpost