Edit: Zero may have played sloppily against Xzax, but he played close to form at least 2.5 of those games against Luhtie.
Zero had plenty of time to adapt, and he actually did on Game 4. I think he was caught off guard initially by Luhtie's more defensive, empty hopping, KEN-esque version of ZSS, but he brought it back. I love game 5s mostly because at that point, each player knows the other person's style, and what their gameplan is, it just comes down to who keeps the cooler head to implement their plan.
In this case, Luhtie was able to adjust midmatch on game 5 to Zero's change in style, and forced Zero into poor options. He earned that set.