Ciao,
to me this seems to be a an incorrect interpretation. A highway=pedestrian is a road for pedestrians who can use the entire road space; vehicles, including bicycles, are not permitted. In an ZTL, roads do still generally have side walks for pedestrians and the carriage way is for vehicles, even though the vehicle traffic in a ZTL is limited to certain classes of vehicles. The details vary from city to city. I do not know the rules in Vicenza, there will be delibera by the Comune. Typically the following vehicles will be allowed: public transport, bicycles, emergency services, residents, electric vehicles, delivery vehicles (at certain hours), motor cycles, tourists that stay in hotels. The procedure for permits vary as well. In addition the ZTL restriction s are different for different times of the day or even different days of the week. An Area Pedonale is a completely different concept compared with a ZTL, and also "orthogonal" to it, in the sense that an Area Pedonale can exist inside an ZTL , but also outside. The tagging for any given ZTL is complex, and, as a consequence, many of them  are mapped incorrectly in OSM. In addition a ZTL can include also areas where only cars of residents in the specific streets are permitted. Another complication can be, as is the case in Padova, that the ZTL is subdivided in zones, and permits may only be valid for a specific zone inside the ZTL.
I have no correct tagging proposal myself for Vicenza, I only noted that your tagging is not correct. If the ZTL in Vicenza is similar to the one in Padova, then you could start with the Aree Pedonali (highway=pedestrian and bicycle=yes/no according to local signs, keeping in mind that an Area Pedonale sign without an explicit sign for the exclusion of bicycles needs bicycle=yes, otherwise bicycle=no. The ZTL could be modelled with conditional access to reflect the time-dependent access rules (If I remember well, the ZTL in Vicenza has fixed time window in the morning for deliveries.) The basic tag will most likely be motor_vehicles=private (this would include motor cycles). This assumes that every moto vehicle entering needs to have a personalised permit before entering. (attention: permit=yes is not correct, because that assumes that anyone can easily get it on request).
 Maybe we should launch a discussion in the Italy forum on this subject?