As an air unit, the Zeppelin unit cannot attack or be attacked. Zeppelins can only be harmed by indiscriminate damage abilities such as Bombard or Shell, or by firestorm. However, if an air unit is ordered to move into a space occupied by an enemy air unit, it will crash into it, killing both units instantly.
The Zeppelin unit can drop 2 Gas onto the space below it. This ability does no immediate damage but reduces the hitpoints of all units on the tile by 1, and deals damage in the decay phase. Since the Zeppelin drops 2 gas, it will spread on the next turn to a 3x3 tile block of gas.
The Zeppelin unit will emit 1 Gas when it is killed.