I recently added a third heating zone to heat a finished basement. With the current configuration, there is 1 circulating pump for all zones and each zone uses a separate Taco 571-2 zone valve. I tested the basement zone and that appeared to be working fine at first. Later I discovered that the 1st floor zone valve was turning on when I set the basement thermostat for heat even though the 1st floor thermostat was set to off. I tried turning off the basement thermostat and turning on the 1st floor thermostat to call for heat and found that both zone valves were on. I believe that I mis-wired the basement zone but don't know what is mis-wired.

Did you use a separate transformer for the zone valves? This may help: vernonwinnelson.com - Taco Zone Valve Chart