OK, lets see, getting certified to teach Zumba. No gym will hire you without a group-ex certification from either ACE or AFAA. Around here, at least, AFAA seems to be the preference. I am blessed to be able to work at the Y under a YMCA group-ex certification, but that won't fly anywhere else. So I am studying for my AFAA cert. And whoo! it's a lot of money. I mean, most professions have certifications, and I think they all are in the same-ish price range, but when you consider that fitness instructors really don't get paid very much...it is a lot.
The Zumba certificate you get for going to a workshop is just a certifcate of completion, which gives you permission to teach a class, call it Zumba, and use the Zumba logo and promotional materials. That's all it does. As of right now, it doesn't guarantee that you know what you're doing, and it doesn't include a group-ex cert. I can't even call myself a "certified Zumba instructor", just a "Zumba instructor", because it's not really a certification like we normally think of things.
That's all going to change next year, I'm happy to say. Right now you can take a Zumba class only to find out it's really LatinCardio in disguise, or the teacher has no rhythm, or worse. But soon we'll have to take a test to show we know what we're doing, and stuff like that. Very exciting! :) I want Zumba to be around for a very long time, and keeping instructors accountable, making sure their classes are really Zumba classes, is so important in making sure we don't dilute the Zumba name, or worse, make it a joke.
If you want to teach Zumba, here is my advice: Start saving for the AFAA Group Exercise certification. Get your First Aid and CPR certifications. The whole time you're doing that, be taking Zumba classes somewhere, or get the DVDs (at least Zumba Advanced and Zumba Power, not so much the Beginner and Abs Buns Thighs, really), and practice practice practice. Then get yourself to a Zumba workshop once you've done all that, because after your workshop you are going to be pumped to get out and spread your Zumba Love to the entire world. :)
Eventually you may want to save up for liability insurance and a good portable sound system (not a boombox--you cannot teach Zumba out of a dinky boombox. Got it?) so you can teach independently, whereas those things are taken care of for you when you are employed with a gym or Y. But those can wait until you've got some experience.
And then? Let me know how you're doing! ;)