I generally try to stay away writing low ratings, especially when I've only ordered from a place once. That said, the stracciatella gelato (my favorite flavor of gelato) was completely flavorless, and I threw most of it out. Store-bought gelato would have been much better, and maybe they should consider that as an option instead of whatever they're currently doing. My recommendation would be to get a cold coffee or smoothie to sip on while you're walking around, and skip on the gelato.
I'm giving Zio two stars simply because it's the only place I found serving gelato in Vegas. Enjoying good gelato on a hot day is one of life's simple pleasures in my book, and the faux-Italy vibe in Vegas combined with the hot desert sun provides a perfect atmosphere for it. Maybe some of their other flavors taste better, but I'm not likely to try again after my first experience.