If you want to use the brand name Zumba and all of the marketing cache that holds, you have to pay the license fees. It has nothing to do with your years of experience teaching dance.
Nothing is stopping you, however, from putting together your own similar format. You just won’t have the marketing machine behind you.
You need to have a license in order to call your classes Zumba.
If you’ve been teaching dance for 23 years, I personally think you don’t need the name Zumba. You are obviously talented, it appears you have a following. If you don’t have the Zumba license and want to teach something that involves latin dance, it appears you have that skill already and you’ve been successful at it.
What makes Zumba, Zumba is the atmosphere, and if you are able to teach an electric, motivating latin-based dance class adding the name Zumba to it won’t make it any better.
If you are excellent what you do, people will come, regardless of what you call it.