In the fashion world, it means to make something better, generally by tweaking or quirking it to better fit what it's supposed to do both functionally and artistically. It's become most popular due to its frequent use on the hit Bravo show Queer Eye for the Straight Guy, usually by their fashion guru Carson Kressly. It is very hard to pronounce, and even harder to spell, many times often misspelled 'jujj' or 'jooj'. Pronounced "zhuj", by the way.
Carson: "Just tszuj it a little, and you're set!"
To tweak, fluff, primp, improve, make fabulous (most often in wardrobe/fashion context, but others also apply).
Pronunciation: Begins and ends with the same "zh" sound, as in "measure".
Made popular by/notable people you may have heard use it: Carson Kressley of Queer Eye for the Straight Guy, Chef Nigella Lawson, Designer Ralph Lauren.
Origin: Variations used in many countries like France, Russia, Scandinavia, Germany, Australia, Canada.
"Just tszuj it a little, and you're set!"
"Tszuj those sleeves!" as in roll-up and make less stuffy/formal.