diymore 18650 Battery Holder Four Li-ion V9 Battery Shield Micro USB 5V/3A 3V/1A Power Bank Battery Charging Module (4 Holders)

Raspberry pi takes up a lot of current and small power supply modules won't do well. Even pi zero won't work well with usual boost converter module. You will need to find a UPS module or get a decent power bank which has ratings of 3A current. I have used this module to power zero 2w https://www.amazon.com/diymore-Battery-Holder-Charging-Holders/dp/B0CBMQ8PZH