If you use Gandi's DNS, you will manage your zone file through our interface:
There are two different places where you can edit or create a zone file for use with your domain names at Gandi.
If you want to change the zonefile from the one that your domain is currently using to another one that is in your zone file portfolio, you can do this online.
Log into your domain's control panel, then, in the lower-right hand of the page, in the “Zone File” section click on the link that says “Change”. It's then a matter of choosing the one that you want from the list of available zones.