>>38213919
Having in mind what we know about his abilities, I think it's safe to assume that he can only command iron/metals, but not the physics involved.
Now, I don't know how the vehicle looked exactly, but between the fact that it is armed, has either tracks or huge tires, is quite big itself and maybe armorered it is quite heavy.
So, even assuming it would work (which is not even sure, as the construction would include plastics, glass, fuel, probably leather, and probably something I forgot, all of which the wizard cannot control) the 'small cube to take with you' would still weigh a lot. If I'D have to take a guess, probably around 3 to 4 tons.
Also, even assuming it would work out and you could carry it, you don't even know if you'd have more space down there, ie if you could use it there. And if that's not case, you would have wasted the wizards energy, as it was previously mentioned, that it tires him out to use his abilites. Furthermore, you would risk not having a way back, depending on how much power the wizard would have to use down there.