You got that right! See here: http://www.etymonline.com/index.php?term=cosmos&allowed_in_frame=0 (This is one of my favorite sites.)
Thank you much for this site. I love googling ethimology of Greek words, and this site seems to be one of the best or just the best
Guess we have the zm thing in other languages like English and Spanish as well, and I think others. ;)
I can only imagine it's the "s" in κοσμήματα. It's just an "s" that sounds heavier before the "μ". Try it. You'll see that : koS mi mata is not as fluid/smooth as koZ mi mata.