Solarpunk technology

Zeppelins largely fell out of use due to limited military application and because fuel was basically free back then due to abundant supplies. I think it is important to keep this historic context in mind.

As for electric quadcopters being expensive, yes, but the proposed business is end to end, so not like an airport that needs to be loaded and unloaded quickly with a large amount of cargo. So for the airships it will be rather pick and load individually replacing not only the airplane but also the trucks delivering the cargo to and from the airport.

It will likely need some good charging infrastructure on the ground to recharge these quadcopters, but the spread of electric cars makes this more realistic these days.