Created a zip file with Linux Mint Archive Manager ... Tried to send it to a collegue via Slack ...

try meatspin.zip

Happened to me too if the file is on a different drive. Move it to ~ and try again

There are actually several ways to create a zip file which can make one file have different contents depending on how a program reads it.

That also enables funny security holes.
If you're interested with a lot of spare time: https://youtube.com/watch/...

Maybe it's a generic error with a misleading message because the file is too large

mv "porn.mp4" "seriouswork.zip"

"leekstreet.zip" might get you better results