Sorry, I do mean Zimbra/ZCS.. Too many apps that start with "Z" at work today
That method will copy over your SSL cert's. It will simply just be like upgrading from your current version to the same version. Or I should say, at least an upgrade hasn't hosed up my SSL certificates yet. If it does, just make sure you have the key/crt's handy so you can re-install, but it shouldn't be an issue.