Specifically, I can't seem to find crossovers relating the four celestial beasts (of Taoist cosmology) to the four elements (which Buddhism uses) :-/. I would have thought there'd be at least something historically (because of interactions between the two systems). There is of course fiction, which is nice and great in its own creative way, like how several anime used the four beasts on the elements (there is this tendency to relate earth to the black tortoise though). Anyway I am both rambling and grasping for words (what a weird combination!), but will certainly post more about it in the forums when I am more coherent.