To be honest with you I'd never heard of Zobrist hashing but then again I've never tried to write a Chess or other such board game for which that it is appropriate for decision trees and such.

I'll stress that the idea of this post isn't to implement a Chess engine but merely to examine an admittedly artificial problem (much like Code Golf results in code you usually wouldn't actually use for anything real because it's typically unreadable even if clever).

Various hashing techniques could speed up comparisons of positions but they don't allow you to store positions.