The following rules apply to units in a Chaos Dwarf army regarding Panic:
Chaos Dwarfs and Bull Centaurs ignore panic tests for breaking and fleeing Orc and Goblin units of all types.
Orcs of all types ignore panic tests for breaking and fleeing Goblin units of all types.
All troops ignore panic tests for breaking and fleeing Hobgoblin units except other Hobgoblins.