Hi booklover!
Welcome back. Sorry to hear about your coach, but it seems a common problem. Glad there are so many knowledgeable people here who can provide the answers that the IP "vendors" don't seem willing or able to.
Can't really weigh in on the zumba part, as I don't do that strenuous an activity, but I can tell you that DH recommends half a packet before a big workout and half a packet afterwards on the rare days when I overdo the walking pace (sometimes it's hard not to break into a run). He claims that it puts fuel into your body for the exercise, then it aids in recovery as you're cooling down.
I'm sure there are other active members who have experience and advice though.