The frames are chalk and cheese. The Zaskar is US built and welded by someone who cares about the joins whereas the Avalanche is built by a bloke with a gun to his head - 'you weld now!'
The materials are different, the gussets are different and the ride is completely different, the too are only superficially similar due to that triple triangle.
Jumping from one to another and riding to work, the Zaskar frame climbs better and makes for a better bike all round.
I've never got on with steel GT's though...