The alternate reality one you are thinking of is 'Crimson Skies', an MS release.
Since airships were fairly invulnerable for a large part of the First World War owing to the fact that they operated at night and flew at around 14-18,000 feet, and it was deemed so hard to get near one that the first RFC guy to shoot one down got the Victoria Cross, I suspect flying Zeppelins might make a rather dull game. When they became more vulnerable to Allied aircraft with Buckingham incendiary ammunition, a better rate of climb and a higher service ceiling, the Germans largely replaced them with conventional 'Gotha' bomber aircraft.
Count Von Zeppelin is on record as saying at the time that: 'The Zeppelin in an antiquated weapon, the aircraft will rule the skies.'
As far as I recall, there are one or two sims in which you can fly a Zeppelin though, CFS3's Over Flanders Fields add-on being one of them if you fancy trying it.
If you are really a glutton for punishment, you could watch the appallingly bad 'Zeppelin' movie with Michael York for some inspiration.

Chock