I want to know if there is a thermostat system that allows two air-handlers in two zones to work in unison.

I have two zones with two air-handlers on the first floor of my house. I want to connect the two zones with an electric baffle and install a thermostat system that would turn on one of central ac systems which would cool both zones. When the one system can not keep up (lets say I get a temp rise of .5 degrees instead of drop in temp) I want the second system to turn on. When the second system turns on it would also close the connecting baffle, as well as open an electric baffle at the plenum of the second system.

Why would I want to do this. I live in new Orleans, and my systems are sized for an 95 degree exterior temperature. When its only 80 outside my systems turn on for a short period of time, and stay off a long period. This has led to a humid environment, and I believe also reduces the efficiency of my units. Two units running for 5 minutes use more electricity than one unit running for 10 minutes.