If you would like to economize by driving, then you really need to re-orient your thinking on where you are staying. You need to stay in smaller towns/villages in the region or in the suburbs where you don't have to navigate a ZTL to get there, parking is free and lodging somewhat cheaper.

Relative to ZTL's, Milan is reasonable, Florence is not - stay away unless you have lodgings inside the ZTL, Rome's is navigable if you know Rome but if you don't watch out.

Personally, I would stay outside of Florence but where you could daytrip in if you wanted. Local train is not expensive and Florence is a pretty easy city to walk. There are plenty of interesting places nearby.