Here's a copy of the Zombie Wars demo, with the winter version of the park tileset:
http://www.mediafire.com/?iufb9eif9v4d6qo
Oddly, the level layout is different than I remembered - however, this has to be the same version I played (found on a coverdisk from June 1997 issue of the "Gambler" computer games magazine).
*shrug*