snip

1. Made sure makeup feed valve was full open.
2. Closed the shutoff on the return line of one of the zones.
3. Opened the drain valve on the inlet side of the circulator. This
allows water to flow from the makeup feed, through the backflow
preventor, through one of the zones, and out the drain valve. Flow was
good and strong.
4. You repeated this for the other zone.
If this is what you did, you pressure purged the system properly, and
should not have significant air in the loops.

Yep, that's what we did for both zones.

We did try one more thing to try to rule out air and/or a frozen line: We
ran hot water through each zone, using the utility sink as our hot water
source. I won't bore you with details of how we did it( unless anyone's
interested ), but all baseboards are working properly, nice and hot. This
also allowed me to verify where the piping goes in the first floor where
everything is embedded in concrete

snipped the rest

I'm now convinced it's the pump, and picked a new one up today. Once I get
the old one off, and prove that it's fried, I'll install the new one

Thanks everyone for the prompt responses!

Tim