I have discussed and debated this question too many times to count. The never ending debate between cardio and lifting weights, which is best for fat loss? If its cardio, WHAT cardio? If it weights, WHICH exercise/s?
I could get really technical in either area, slow and steady cardio versus interval training, treadmill versus cross trainer; squats versus walking lunges, high repetition lifting versus low reps and heavier weights...but my honest, bo BS answer? WHATEVER you can consistently do!!!
If you enjoy Zumba and you can do it regularly and consistently? Then Zumba is the best choice for you. If you enjoy lifting weights and hate cardio, DO THAT!! To honestly lose body fat and make lasting body composition changes, you need to consume fewer calories than your body needs to maintain its current weight, get sweaty for 30 or more minutes at least 2/3 times a week, and choose foods that do not cause inflammation and cause water retention...i.e cut out the junk and choose whole foods.
When you get on the journey of reducing body fat to lower levels, as in fitness and bodybuilding competitions, this is where we get into the nitty gritty of manipulating carb timing, macronutrient breakdowns. However, for most, to maintain a healthy weight, we just need to cut out the junk and move consistently, and as your body adapts to the level and intensity of exercise you are doing, move the goal posts a bit, do a few extra minutes, reduce your rest between sets, increase your weight, reps. Doing any one of those things will increase your intensity.
So, the moral of the story is...K.I.S.S, keep it simple stupid!! Do the basics well and you will be most of the way there!! Yes you need balance in you life, as one of my clients always used to say, "You have to live too!!", so it will always be a trade off, the amount of effort put in will be in proportion to the results and changes you see, but THAT is a topic for another day!!