The lyrics of the "first" Zydeco song went somthing like this:
"Les haricots sont pas sale'" ~ "The snap beans are not salty."
So, the "Z" sound is actually the "S" in "les." In Cajun French, just as in Parisian French, the "S" sound at the end of the definite article "les" is silent when the next word begis with a consonant. but is sounded when the next word begings with a vowel.
Jim, sorry it took me so long to look back at this thread and respond about those snap beans. I'm sure you're right on the money in regard to "Gumbo z'herbes," by the way.