Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to their inherent high energy density and low cost. However, practical applications of this technology are hindered by low power density and short cycle life, primarily resulting from large polarizations and non-uniform zinc deposition. Here, we present a systematic study to decode the sources of voltage loss and demonstrate that by judiciously tailoring the key components (electrolyte, electrode, and membrane) and operating conditions (flow rate and temperature), the performance of ZBFBs can be dramatically boosted. Our results show that the optimized battery exhibits an energy efficiency of 74.14% at a current density of as high as 400 mA cm-2 and is capable of delivering a current density up to 700 mA cm-2. Furthermore, a peak power density of 1.363 W cm-2 and a notable limiting discharge current density of ~1.5 A cm-2 can be achieved at room temperature. More remarkably, the battery can be stably operated for over 1200 cycles (~710 hours) at room temperature at 200 mA cm-2 and 60 mAh cm-2, demonstrating excellent cycling stability. The data reported in this work represent the best performance of ZBFBs in open literature, which will shed light on the development of high-rate and long-life ZBFBs for next-generation energy storage.