This DVD by Michelle Joyce claims to be a complete introduction to zills, from the very basics to dancing with finger cymbals.
It's well presented and clearly explained, so in my book it fulfils that promise - but a word of caution: I've heard a couple of beginners complain the beginning drills are just too fast for them to follow.
So, if you're not already familiar with the basic belly dancing rhythms, this DVD might be too challenging for you - but if that's the case, perhaps you should reconsider whether you're ready to add zills to your repertoire just yet.
For the average beyond beginner/intermediate about to embark on playing the sagats, it's a good choice in my view.
I still think Tobias Roberson's Finger Cymbals DVD is the best buy, because it has so much material you'll keep coming back to it for years. However, if you want a DVD that also gives you some dance practice with zills, you'll need Killer Ziller.