Rental car logistics

It seems from your other posts that you are not an EU resident, therefore you are unlikely to have an EU Driving Licence.

If that is the case, every driver on your rental needs an IDP to accompany their home licenses. If you are North American you can get them at AAA/CAA offices.

Every city, every town, and most villages have one or more (Florence has bucket-loads of them) ZTLs. Become familiar with the signage to avoid those expensive souvenirs. If you understand the concept, and recognise the signage you won't get caught out.

Milan has a huge "Area - C" ZTL. Best advice - do NOT drive in city, town or village centres. Somebody has said that Greve doesn't have one. That would be the exception. There's even one in Varenna.

By the way, there may not be a ZTL in Greve but I've just looked around on streetview and there certainly are plenty of no-entry signs. You do understand what the different road sines mean? You often don't see words on signs, you need to understand the graphics. Round white sign with a red band around the outside, in this case.

You do not mention your allotted time, but for just transportation, stay on the train until Florence or nearby. You might even go to Florence, then train to some point, specifically to pick up a car. Use your preferred Rental carrier to search for locations, if you have no preference, Hertz, Autoeurope, Europcar, and Sixt come up as ones many use. You might look at Empoli, the Florence Airport, Siena, among others. I would just consider renting and returning to the same location.

As for ZTL's or the restricted zones, they are essentially everywhere, maybe even Greve. Just assume that any town you approach does not allow driving in the town center. Park in the lots just outside the city or city center and walk or take a bus the rest of the way. Get familiar with traffic signs, including the ZTLs.

Yes, we are US residents. And I did realize we have to get a special license but I very much appreciate the reminder and the advice!

Picking up in one location and returning to a other does NOT usually come with a huge dropoff charge ( but check your specific trip just in case)
However, dropoff instructions are sometimes sketchy so build in extra time for that -- especially to a train station. And try to get details. (For instance. Hertz in Orvieto gives the street address for its rental office, but the actual return lot is across the street -- and not well-signed.)

It's also a good idea to note the hours of operation of the location you'll be returning car. Some of the locations in small towns are closed from noon to 3pm. Not only for actual travel purposes but for when you search, if you enter a drop off time during closed hours,it might impact availability of cars and locations.

If you don’t absolutely, positively need to drive then just forget the rental car and use trains and even an occasional taxi or uber or Lufthansa.

See opinions on this similar thread from last week: https://community.ricksteves.com/travel-forum/italy/picking-up-a-rental.

As for ZTL's or the restricted zones, they are essentially everywhere, maybe even Greve.

Don’t confuse the issue with speculation. If you do t know, don’t say. I know from experience Greve doesn’t have a ZTL. However, it is far more convenient to park in the free lot just a block from the piazza.

I also know the many of the nearby towns do have a ZTL, but they are well marked and easily avoided.