Multi-zone hydronic boiler question: zone valve to better isolate zones?

Our NYC town house has a boiler with two zones; one for the basement and one for the first floor. Each floor/zone has its own thermostats and all is in good working order. Problem: the basement thermostat is on (and requesting heat) more often than upstairs, and we're noticing that when the basement zone is on, the first floor baseboard pipes are often also hot, which is unpleasant and undesirable.

We had a plumber come out and take a look and after some discussion it seems like our cheapest option is to install a single zone valve for our first floor (upstairs) zone so that when the upstairs zone's thermostat is off, it is preventing any accidental cycling through the upstairs pipes caused by the other zones' circulator.

This seems like a workable and sensible solution but I'm new to this stuff and just wanted some validation that this should do the trick. Also for what it's worth, parts and labor will be $700 after some haggling and bulk pricing with other stuff we need to have fixed. (Parts include the zone valve and apparently some "relay" to control it)