Unlike official updates from Siemens or HPE , repacks are not usually vetted for malware.
Employing tailored Smart Queue Management (SQM) algorithms to maintain smooth online gaming and video streaming latencies under heavy network loads. Stripping Bloatware and Optimizing Memory
If the device boots normally into its broken state without updating, your USB drive might be too large or partitioned incorrectly. Try a smaller drive or switch ports.
Generic flashing tools will reject a mismatched header. The "repack" part of your keyword implies that you have a source firmware (perhaps from a different but similar device) that needs to be restructured to fit the zsz53rla81 bootloader’s expectations.