[quote=Chev]
...I just realized something. Wouldn't the Eight tales and the other tailed beats be familiar with Zetsu type chakra since he was exposed to it back during the Fourth Great Shinobi war? I'm not going to act on that or anything, Just pointing it out. xD
[/quote]

They may have encountered zetsu's before but a zetsu's chakra itself can't be sensed. The only one who can sense a zetsu is the one who created it. Hence why zetsu himself was able to spy on everyone without getting caught. He couldn't be sensed.