I'm with those who believe the show became far far too much a Doctor Smith show, but halfway through this one I wished Jeremiah Smith would disappear and Zachary would show back up.
This does occur later, but Zachary is offscreen for quite a long time. I don't know anything of this actor Henry Jones but he had a lot of credits and apparently warranted a lot of screen time. It didn't work for me at all.
As the other reviewer notes, the character is insanely out of place. It's literally as if he wandered onto the wrong set after costuming. The whole parachute thing conveyed this was supposed to be a silly romp episode but they should have dressed him for the right century.
I've been going through the whole series and forcing myself not to skip, but this one was quite a slog.
A few chuckles here and there, like the huge gambling machine chasing the Smiths.