You can go with the 3/4 copper to the outside because it is a short distance and also a 3/4" backflow device. I would go with 1" valves and manifold and 1" poly to the sprinkler heads. It's not that much more money and the flow characteristics are much better. We, on a regular basis flow 10 GPM on a 3/4" copper service and we always use 1" poly. I'm not familiar with a 32SA head. Must be Home Depot??? Your good on your head count and spacing. Three rows with heads evenly spaced, (9). The nozzle size for the 4 half circle heads should be approx. twice the size as the 4 corner head nozzles. likewise the 1 middle head should have a nozzle that is approx. 2 times the size as the half circle head on that zone.. You should be able to do this safely with 3 zones. Look at the rainbird 5004 series head.

homr,

Thanks for your response. It seems counter-intuitive that you would benefit from increasing the pipe size when you are already restricting the flow upstream. I know you're correct but my brain doesn't get it.

So do you go from 1" poly to 1/2" funny pipe/risers? Or do you go from 1" poly to 3/4" and use 3/4" NPT heads?

Thanks for the head recommendation. The 32SA are cheap on Amazon but seem outdated now. I was looking at the 5004 series last night.

I can not see your property, do not know anything about your elevation changes, service line length etc.etc or anything that might affect your pressure losses, so thats why I suggested to just go with 1". You cannot control what size service line or inside plumbing you have but you can pipe size what ever you put in after you tap the source. Larger pipe will lower the velocity of the water as well as minimize any pressure losses from that point on. 7-8 GPM is about the max you would run in 3/4 poly.
Yes, you would tap off your poly pipe with a 1x1x1/2"ft tee and run your funny pipe to each head. Rainbird 5004 heads are 3/4" thread. #/4" poly would work, but you had better have your hydraulics correct.