A software policy specifying the agent install file at http://yourcore/ldlogon/mac ought to be enough if they're not too far out of date. Try that and see if it works.
If they're really old, you might have to do some extra stuff: http://www.droppedpackets.org/macintosh/upgrade-mac-agents/
A .zip file is a valid package type for macintosh. This means that you can create a package based on the file in the ldlogon/mac directory. Then you can create a policy delivery method for that package. This will update the client for you.
Thank you for your answers.
What command I have to use in the package, to install the .zip-file silent on Macintosh computers?
You don't need any command -- the mac client tries to extract and execute anything you give it.