Aluminum in the interior wall of a Zeppelin is unlikely. It is most likely paneling stapled and/or glued to wooden studs, probably 1x1 or 1x2 to provide a 1-inch hollow wall. These are usually fastened to outer wall, floor and ceiling to serve as a bulkhead and contribute to the rigidity of the assembled box that is the trailer.
RV construction varies greatly with type and model. Keystone used foam core panel walls for the Zeppelin, with aluminum tubing forming a perimeter frame and a few verticals, to stiffen the finished panel. I don't remember the rest of the details, no longer have those brochures, but know this model is priced way below what it costs to build with full aluminum framing (as used by Excel, Carriage, New Horizons).
