How long did a transatlantic flight take in a zeppelin?

The Graf Zeppelin cruised at 80 mph. That was pretty much in the ballpark of how fast a zeppelin cruised. Considering the distance between London and New York City is 3459 miles, that would yield a flight time of 43 1/4 hours.

airships.net/lz127-graf-zeppelin/size-speed no longer exists

The maiden voyage of the Hindenburg across the Atlantic took 61 hrs 38 min from Friedrichshafen in Germany to Lakehurst NJ, a distance of 4,381 miles (7,050 km).

http://www.airships.net/hindenburg/flight-schedule/maiden-voyage/passenger-account

https://en.wikipedia.org/wiki/R100
The first transatlantic crossing by an airship was by the privately designed and built R100. (Chief designer Barnes Wallis, chief stress engineer Neville Shute Norway the novelist).
" R100 departed for Canada on 29 July 1930, reaching its mooring mast at the St-Hubert, Quebec Airport (outside of Montreal) in 78 hours, having covered the great circle route of 3,300 mi (5,300 km) at an average ground speed of 42 mph (68 km/h). The airship stayed at Montreal for 12 days with over 100,000 people visiting the airship each day while it was moored there, and a song was composed by La Bolduc to commemorate, or rather to make fun of, the people's fascination with R100. It also made a 24-hour passenger-carrying flight to Ottawa, Toronto, and Niagara Falls while in Canada. The airship departed on its return flight on 13 August, reaching Cardington after a 57½ hour flight."

With such slow airspeeds, Zeppelins flew with the winds. Into a headwind the craft hardly advanced. They flew with the winds to their back to get those noted 80 mph velocities. They commercially tended to follow a great circle route (not the great circle route of modern planes). That route took advantage of prevailing winds as much as possible. They crossed the Northern Atlantic East to West, then South toward South America, the route continued West to East across the Mid Atlantic across to Africa then North back to Europe by several routes. So their speed varied greatly even for a single ship. They needed to tack against the wind which reduced forward velocity a lot.
https://en.wikipedia.org/wiki/Zeppelin
So, a transatlantic flight took many different times depending on whether it was an East-West flight or a West-East flight and which parts of the jet streams it encountered.