A Zuora subscription may have many versions as it is amended, some of which can be in the future (ie.
A Zuora subscription may have many versions as it is amended, some of which can be in the future (ie. downgrading from a paid tier - because we don't refund that user, the downgrade is instead set to the point in the future when their paid period ends).
The Zuora API does not explicitly tell you what the *current* subscription version is. You have to work it out, by looking at the 'amendments', finding the first amendment that has yet occurred. That amendment will give you the id of the subscription it modified - and THAT will be the *current* subscription version.