zombies used to be a huge problem in the ruins of Old Chicago and St. Louis before the CS wiped them out
The traditional ritual-created zombie is too troublesome to make for me to believe they could be a huge problem. Creators are usually going to put them to work rather than lurk in ruins.
As unspecific as this statement is, I guess it could be a wide variety of zombies the CS wiped out in the last 80 years. Could it have been Brulyx?
That would be quite the chore for the CS. Energy immunity, MDC, vibro does 1/3, need called shots to hit anything besides torso, 20% max chance of hitting head or neck...
Fire is the only saving grace I can see. The plasma cannons would be the go-to. Would only be a problem if someone gave them permanent impervious to fire charms