Zelon and Z-Lon are exactly the same. Zelon is sold by Blie Ribbon Flies. Z-Lon is sold by Betts/Umpqua Feather Merchants. Get your Zelon from Blue Ribbon Flies. The price of Betts Z-Lon is highway robbery for a tiny bit of yarn. You'll get more Zelon yarn from Blue Ribbon Flies at a lower price.

Z-Yarn is similar but not the same. It is slightly finer, more opaque with less translucency. It is not as bright or as coarse as Zelon/Z-Lon.