{my first post, yippee!} I'm a Zumba instructor at my gym, and agree that it's a great workout. (as an instructor I don't get paid by the company, in fact I have to pay big $$ to be certified! but that's another discussion entirely
) It really gets my heartrate up, and in most sessions I burn at least 700+ calories and hour. YMMV, of course!
I've had people say that it's not that difficult, though. As with all exercise, it's how much you put into it: move your arms more, make the moves exaggerated, etc. And if it doesn't "float your boat," then there are lots of other great videos out there that might! I can't recommend a particular video, since I'm not terribly familiar with the home workouts.
If you do this particular form of workout at home, make sure you have little or no tread on your shoes, and watch out for carpet. Ideally, I would recommend a hard surface but we have to work with what we have! The pivoting on the feet can really torque the knees if you have too much traction on the feet. I use two different types of shoes when doing Zumba, one for home (that has ZERO tread) and another for the gym (has a little more tread, more suited for the wood flooring at my gym).
Good luck! Happy dancing!
{I hope this doesn't come across as "shilling" --> there are good and not-so-good things about all the exercise formats out there, just hoping to offer some helpful advice
}