This is about the anime characters. For the monster itself, see Zuum.
The Zuum troops are not quite so cowardly a bunch as some of the other baddies, but they are pretty good at sizing up opponents and know when they are outmatched.
The Zuums seem to prefer the coast, and first attack the Searchers in Episode 15 when Gali sends them to ambush the team in the abandoned port city of Polo. Captain Horn has to drive them off with his ship's cannons.
After Gali falls, the Zuums begin working for Naga, and can be seen working in his castle on numerous occasions. When the Searchers finally reach his fortress, Captain Zuum and his troops storm the courtyard, and only cease and desist when they realize that their master has killed himself. Trying to avoid more bloodshed, they retreat again.
After Moo's destruction, the remaining Zuums begin working for Durahan in Episode 62, where they again attack the Searchers near a port city. This time it appears that they have no Captain, and instead take orders from Poison.
Next Poison rallies their pack to help attack the Searchers when they arrive in Kawrea, expecting that Gali and Sandy will help them. Instead, they realize they will have to face the combined forces of Genki's team and two of the Big Bad Four, and the Zuums wisely retreat.