We have been running from Live CD and usb drive for 3 years without issue.
I’d use a good quality drive though and keep a backup via web gui whenever you change config.
We have 5 x connections and 600 computers so a big site.
As long as you use EXT3 for the flash drive you will be fine. If you use fat32 then an unclean shutdown of zs will nuke your config.
The other options is to use VMWare or similar. We have another ZS working under VMware workstation and it’s perfect. By using VMware all modern hardware is supported as older hardware is emulated and passed to ZS. There are premade VMware ZS images to download.