Believe me, low carbon intercontinental travel is ships. Like normal, mundane, boats.
Boats can lift so much more stuff for the weight of the craft and support that it is not even fair.
A container ship can lift about 10 times the weight of the ship as cargo.
I don't have stats for airships but my guess would be it is reversed, so no more than 10% of the weight of the airship in cargo.
Also, each airship can only lift very small amount of cargo so a single container ship can probably transport as much stuff as all the airships we will be ever able to build combined.
If you don't care about how much cargo is used, then you have sailing ships which we know quite a lot about. You can sail long distances without using a drop of fuel.
If you stick to container ships, you still have net zero options. We can use expensive hydrocarbon fuels made from renewable sources and drive those ships at slower speeds which would lower fuel consumption. This I think would still be so much cheaper than airships given the costs to produce and maintain those.