Redis doesn't compress contents of lists (or hashes or zsets) in a "ziplist", it packs them in a concise manner that omits structure overhead.

Source: the source code of Redis itself https://github.com/antirez/redis/blob/unstable/src/ziplist.c , Redis documentation: http://redis.io/topics/memory-optimization , and/or my book: http://bitly.com/redis-in-action .