Ciao Linda!
if you have a reservation in a Hotel which is located inside the ZTL you should check with the concierge if the hotel has a Parking directly or if they have a special agreement with a private parking closeby.
In both cases,
you are welcome to drive into the ZTL (NOT IN THE PEDESTRIAN AREA, be sure you do not get inside it) and your hotel staff will immediatley inform the COMUNE DI FIRENZE about your vehicle license plate number to have it removed from the list of cars which entered under the cameras (they limit the access to downtown area). Don't worry, if it is Sunday, you are right there are less restrictions but you are allowed if you are registered at a central hotel. You can simply INFORM THE HOTEL STAFF that you are coming by car and the license plate number.
I am attaching you a couple of links which refer both to driving suggestions in town and the Map of the ZTL.
Link to DT article
Map of ZTL
If it is Sunday the cameras are not active: if you decide to park in downtown Florence please read the following useful
detailed map/article.
For your visit in Florence: the city center is not that large, but considering your special necessity I would suggest you to use a
rickshaw. Touring Florence with a someone who can easily accompany you into the pedestrian area would help you save time, energy and will guarantee the smoothest experience! I had the opportunity to accompany lots of guests on my bike and to book for them a rickshaw so that we could easily cover four districts of Florence in a couple of hours without any sacrifice. I remain at your complete disposal should you need any further info about it! Looking forward to meeting you in my hometown, have a nice Sunday, Elena