you should probably specify the -o information prior to the address info i.e.
mount -t cifs -o username=<USER>,password=<PASS> //<share-address>/<share-name> /mnt/mount-point
As for why it is err-ing out, this could be due to your username, it seems like you are specifying the domain with the user, which is how you mount a share on Windows but not the same on unix, it should be just the username, if you want to specify the domain, add it to the end of the command like so `username=user,password=pass,domain=example.com
So in your case try using:
mount -t cifs -o username=Administrator,password=zen,domain=Provisorio,noserverino //10.20.30.1/zmg /mnt/zmg
another reason the error 13 is appearing is due to folder permissions, so make sure you have the correct permissions on the wondows folder. for testing i'd say open the permissions up first to eliminate it as a possible cause!
To make this a permanent solution i.e. making it persistant after reboots add this line to the end of the
/etc/fstab file ( you will need sudo permissions to edit this file! )
//10.20.30.1/zmg /mnt/zmg cifs username=Administrator,password=zen,domain=Provisorio,noserverino 0 0