Reboots during flash can indicate the necessary partitions aren't being mounted. Prior to install you can " df" in an adb shell to view whats mounted, if nothing "mount -a" or mount partitions individually "mount /data" etc. Make sure everything is mounted before install.

If you install successfully you can go back into recovery after bootloop and check if /data is populated with system.img, system-data, user-data, android-data.