I think its clear that against the players 3 years older or more, Quinzi will struggle to play more than 1 tough match in a week at the moment. Conditioning obviously comes with the older he gets, he will be able to last longer playing in weeks like this.
Signs of a bright future. Would be fantastic to see a new italian star. But let's not hurry, he has still much to learn. Many more years to learn and probably won't be easy at all. I don't know much about tennis academies in Italy, but he surely has a big support now by the federation.