vCenter 8.0
When the ZIP header is interacted with, for example a firewall unzipping and rezipping it, this can result in the ZIP header no longer being recognizable in vCenter. The contents of the ZIP are still fine, however the compressed file is no longer usable.
When testing whether a package is a valid update on a computer outside the issue, you will need access to the download source. Testing with the same downloaded file that previously failed will still result in an error since you are testing with a ZIP header that has already been interacted with.