Your marketing department clearly has no respect for your customer base. Once again your company has taken a well-established product with a loyal customer base and "improved " it.
I for one bought a lifetime supply of the new product from a vending machine. Flat, too sweet, and a chemical aftertaste. I will change back to my pre-Coke Zero Diet Pepsi for as long as it takes for you to realize and admit to another stupid move.
The former New Coke events are a cornerstone case study in business schools as a marketing disaster. One would think the new generation in your marketing and R&D departments would want to avoid a repeat. But here we are.
You may attract a few new customers but you will lose other loyal ones. If you wanted to bring a new product to market, do it and have both the new and old customer bases.
And do you really think your customers are so stupid as to not realize that Coke Zero was zero calorie/sugar. Your customers aren't stupid. However, your marketing executives appear to be.