zoining my gas crown boiler

hey guys,
first time posting plz help. I have a one loop heater system thought my entire house and i want to zone my home to three zones (first floor, second floor and attic). My question is that i have 8 cast iron heaters on the first floor, and was wondering if i should loop all 8 heaters in series on the first floor or can i have a split supply and a split return on the first floor zone, to split to heaters equally so all heat will be heated at the some rate.

I'm not sure if i split one zone to have two supply and two return if its going to be better than having all 8 heater in series in one zone. Also what
size and type of pipe should i use for the zones manifold.

any help would be appreciated, thanks

Radiators do not work well on a series loop system. They should have a "circular" main line with "MonoFlo" tees and valves on each radiator. I have no idea what your poll is trying to "discover", so I didn't vote on it.

Depending on the piping, zoning could be expensive and difficult.