China 1st Dec - Vietnam 5th Dec
Yeah, you must have a vehicle capable of flying then! Because coming overland from Nepal, in between those two, is a road distance of several thousand kilometres (maybe 4000, or even more?) plus the highest mountain range in the world, and the 4-5km high Tibetan plateau... and as we all know, December is winter in the northern hemisphere!
Even if you could do it weather-wise, which I doubt, you´ll still have to deal with the massive bureaucracy, to get your vehicle into China. Not impossible, but also not possible just by popping up at the border, and you´ll need to use a tour-operator inside China, arrange everything well in advance, etc. Search this site, there´s plenty of info about all these here.
Entering Vietnam with your own vehicle would be yet another challenge which, in case of motorbikes at least, is very unlikely to happen, cars or flying vehicles I dont know - but I´d first worry about that getting into China & crossing the Himalayas in midwinter-part.
A more realistic option to bypass Burma is shipping your vehicle from Nepal or India to Thailand or Malaysia.