Whoa, so each one of those twelve characters could potentially field a ten-thousand CS army? And each could be worth as much as thirty-thousand CS? That is insane!
Be glad you weren't around BT for the Fourth Invasion. We were absurdly,
insanely outmatched.
From what I have seen, the Zuma field a mix of daimon and monster units. Both are bad. The daimons tend to either be very long-ranged SF units (dishing out thousands of hits at 5+ lines away) or apocalyptically powerful cavalry-type units that can fly (and charge) over walls. One unit of charging daimons can devastate an entire army's infantry line. Also of note, they have no discernible morale and units will fight to the death every single time.
Monsters are another story. They're less explosive in terms of damage output, but also far harder to kill and they can come in truly obscene numbers. Monster armies have no special capabilities I'm aware of, they're just really big and really tough. They will outlast you in combat. Their weakness is relatively poor morale. The way you win against them is by making them rout before they grind your army into bits, which is exactly what will happen to you if they don't rout.
It's extremely hard to estimate daimon and monster combat-effectiveness because the units tend to vary considerably in different times and places, and are not always consistently named. It's entirely possible that the Zuma units have customized capabilities that make them different than their BT counterparts, but I would guess that there are similarities to the basic outline I have described.