How much of a difference

Unfortunately you're looking at a fairly large difference in scale to incorporate into one dio. The only way that I've seen it work was in a forced perspective dio that made the smaller scale vehicles look much further away from the 1/35 vehicle.

I agree with shermanfreak, it would be hard. But you might try something like a shadow box diorama so people can only look at your display from one angle, putting the larger scale stuff (1/35) in front and the smaller scale stuff (1/48) farther back. Probably something similar to what sherm had in mind Would probably wind up pretty large though...
Good luck and let us know what you come up with.
William

As the distinguished gentlemen have already mentioned, the forced perspective idea is a good one with the different scales.
If you want to show them side-by-side, the difference would be very obvious between 1/48 and 1/35.
Unless you're doing some kind of nutty Twilight Zone diorama, featuring giant armor or shrinking aircraft!.

Oh.. I loved that show... Land of the Giants or something like that..?

A agree what everyone else has said. It would be difficult but if you managed to put the aircraft away from the armour it may work out

Forced perspective is quite common in model railway circles to give the illusion of depth, especially on narrow models.

Perhaps the armour in the foreground, with the aircraft behind in the process of attacking. It all comes down to fooling the eye, therefore a low eye level, looking up past the armour.

It could work!!

Karl