The development of zeppelins will proceed normally until the last years of WW1, when Graf von Zeppelin will complete a new and much larger zeppelin (around the size of the Hindenburg) ahead of the historical timeline. By stealing developments by Tesla and Eccles he will equip the zeppelin with better engines and power, making it a much more usable craft. After the war Graf von Zeppelin will flee to the USA, but at the same time he will help orchestrate the Kaiser's theft of the German zeppelin fleet.
Over the next 8 years he will continue to develop zeppelin design ahead of the rest of the world, and will pass these on to the Black Baron where these advances will be made reality. By 1925 the Black Baron will have zeppelins big enough to lift 1 million kgs dead weight. By 1930 they will have zeppelin carriers equipped with heavier than air craft that can launch from them. By 1935 they will have zeppelins with IonJet engines and droneJets using Tesla's discoveries in propulsion and remote control. They will control the air where-ever they are, but their numbers will be their limitation.
The major powers will be slow to realise the impact of this technology (as they were for aircraft carriers and airpower), and accordingly zeppelins will have as big an impact as dive bombers and aircraft carriers did in WW2, only 20 years ealier.
Nikola Tesla theorised the possibility that electric charge could be used to ionise air and control its movement to provide lift and propulsion. In the game this is taken to its extremes and Tesla creates the IonJet engine. This can be constructed as small as personal rocketpacks and as large as jet engines to propel huge zeppelins, or drone aircraft.
The only draw back to IonJets are that the air they use is toxic for a short time after it is expelled, requiring good ventilation or gas masks, or both. The other limitation is that the engine requires a very large electrical charge to startup, but only a small charge to maintain. Because of this they are usually launched from a base station with the appropriate capacity. In an emergency some engines can be dropped from a great height and can use the fall to generate sufficient charge to kick start the engine, but this is risky.
Rocketmen who intend on landing and thus needing a re-launch will need to take a battery-sled with them, to be used to startup their rocket packs.