After a long trying I got that the .zip should be of the contents of the zimlet folder and not of the folder+its contents.
After I understood that I have been able to deploy a zimlet.
After the deploying I stopped/started zimbra, logged in as a common user and I have seen there was a typo in the zimlet. I corrected it on the source, created the .zip and tried to deploy it again but the server failed. So i removed the zimlet in the command line. But nothing. I changed the version .xml from 1.0 to 2.0 . But nothing.
How can I do it after the first time?