Signing Key Google Play

Tried to upload an app to production from Nowa Cloud, but couldn’t get it to work.

I generated a key from Nowa, which gives me a key.jks + file with alias & passwords.
First, you need to upload a key.

I needed to create an output.zip. After a whole hassle to get the correct Java JDK to create that output.zip, I still get an error.

Would like to add some extra images to my post but couldn’t.

Any thoughts?
Thanks!
Thomas