Snapdragon 835 chipset which has a built-in LTE Cat. 16 modem, you are mistaken. ZTE touts its homebrew "independently developed Pre5G Giga+ MBB solution" as the culprit behind the phone's 1Gbps download speeds achieved in lab environment.
How does the new ZTE flagship hit these speeds? Well, the Snapdragon X16 LTE modem, utilizes a combination of carrier aggregation, 4x4 MIMO antenna technology, and 256-QAM modulation to achieve LTE download speeds that are up to 10x faster than first generation LTE devices that only supported speeds up to 100Mbps.
All this fine and dandy, but good luck finding a carrier that can provide you more than first-gen LTE speeds to your "pre-5G" Gigabit phone. Other than the fast download speeds thanks to the Qualcomm chipset and ZTE proprietary network tech, though, the phone itself wasn't shown, as it is not even enclosed in a retail chassis yet, just the case mule you see above. Good, fast times.