Thanks for the feedback. I think I am going to explore the master valve & flow control set-up. I have actually take water pressure reading for each zone, but cannot recall what the pressure is when each zone runs. The 4 sprinkler uses more pressure than the other two so I might remove one of the sprinkler heads in the back (reducing 4 to 3) as well.
Rain bird brass valve $78.09
Hunter-Sprinker-Flow-Clik-Sensor-Tee $172.44
I have not decided which controller to get yet.
Upon further research, it appears my PVB probably won't meet the backflow requirements when using a fertilizer injector. It looks like I need to get a Reduced Pressure Zone Assembly. Not sure how difficult these are to install. I might open a new thread to discuss this. I have seen other posts regarding installation, but could use some additional feedback as well.
I saw this 'plumbing circuit breaker'
http://www.flologic.com/flologic-guide/FloLogic-3.0-Feature-Specification.pdf used on This Old House, but I don't want to spend $1500 on such a system at the moment.