Airliners carry a lot of fuel. The wings are fuel tanks, and there are more in the belly. There's so much fuel they cannot even land after takeoff without dumping it.

> Moreover, there isn't a way to design a hydrogen-based zeppelin that can both use hydrogen for buoyancy and hold it safely; even today containers for gas hydrogen are bulky and heavy.

Of course there is a way. The Hindenburg's dialectric problem could have been solved. It's frankly incredible how good we have gotten at making airliners safe despite being pretty much a flying bomb. See the 9-11 films of what happens when two of them, loaded with jet fuel, hitting a skyscraper. Those fireballs weren't from materials in the buildings.