This one WILL require some planning. The terrain is not for the faint of heart. You should for your own safety sake know the basics of mountaineering, have proper gear and a certain level of fitness will help.
Start the hike in Hammersbach (750m) and head for the Höllentaleingangs lodge, then through the Höllental gorge (truly breathtaking) to the Höllentalanger lodge (1.379m, great place to stay over night). From here continue towards the Zugspitze. The cache, RubberMaid type box, is covered with rocks at an altitude of 1.910m. You should plan around 3,5 hours to reach the stash (excluding any beer breaks).
From here you can continue to the Zugspitz summit or return. Keep in mind climbing down is considered to be somewhat more difficult. Carrying on to the summit you'll need at least another 3,5 to 4,5 hours of steep glacier and rock climbing. If you can't stand heights then this is not for you. The entire route is manageable and steel ropes can be found in most places.
This cache is the first of a series of high alpine stashes. Full details, hints and Pictures on our website http://www.gps-club.de