Board Thread:Questions and Answers/@comment-5239435-20130206201307/@comment-6553047-20130222065451

Yah the Anime Arc for Zanpakutou already stated that a Zanpakutou is born with, lives alongside, and dies with their Shinigami. When the Shinigami ceases to exist, so does the Zanpakutou. The only way a Shinigami can have the Zanpakutou from another is if they were an identical clone or something.