To get right to it, there are not really multiple certifying agencies for Zumba. As I understand, Zumba is a registered trademark of Zumba Fitness, LLC.
So therefore any trainings can be found by searching at www.zumba.com/trainings
Sometimes it’s easiest to speak with an actual person from the certifying agency. If that’s something you agree with, here’s some information directly from Zumba’s site:
“Customer Support is available from 8:00am to 8:00pm EST, Monday through Friday, excluding holidays. Our U.S. Customer Care telephone number is 954-925-3755.”
Hope this helps and best of luck to you!