Now, if Vash hadn't known Zazie, the first time around, he would've taken Allen as someone who wouldn't even be able to wrestle a tomas calf; but, luckily enough, Vash did know Zazie, and, as such, was as relatively prepared for the attack the first time they'd sparred as he was for the second time.
That was to say, he was perfectly ready. But, ack, he'd have to watch the 'invention' thing - one wrong step into that looked like a death trap - so he stuck to the basics. Twisting with the same reflex he'd done to avoid millions of bullets, the Stampede was quick to get out of the way (and hope Allen didn't get caught in his coat tails: he really needed to fix those) and prepared his own counterattack...
... Which, in Vash speak, meant skidding to a stop a good distance away (enough for Walker to, say, get a decent build-up for another kick) and then being in position to quickly bring up his arms for a block. Either that or just plain watch for the next move.
At least they were both smiling- er, smirking, as it appeared to be in Allen's case. This... wasn't as bad as he'd first thought it would be. 'Fighting' and 'innocent' rarely went together.