backup of dns files ??

is it posibel to add backup of *.dns files to ??

No, *.dns is not backedup. The DNS is rebuilt from scratch. You may however take manual backup of dns files.

so, this means that if there are any customizations to some DNS zones, after restore they will be lost right ?
If this is the case maybe you should revise this issue.
I provide hosting to specialize programmers and they are always customizing their DNS zones, it would be really bad for me telling them all of their changes are lost.

All the changes made outside HC are not retained. Anyway, I have forwarded suggestion to developers.

Dear HC Support,
I think we need to request that the backup/restore of DNS be an OPTIONAL component. I would like to see a restore feature that permits optional restore of each and every dns entry.

Also, on the mysql issue, any way to code the interface so that we can easily add mysql databases that my have been created prior to HC install or "outside" HC ? so they may be included?

If you click on the Advance button on Rebuild Option dialog you will notice that you can disable DNS/Mail/DSN restore for individual domains.

You can manually add mySQL databases to the mySQL database in HC database.