Your comment about Zurich makes me wonder whether the transaction taking place is in a different currency to that of the card

If so, this is not a Hertz problem but a card company problem. In this situation, an authorisation for the amount of the purchase is taken ; when the transaction reaches the account with any conversion fees/changes in exchange rates etc it is common for the local currency amount not to be identical to that of the authorisation. When the amounts are not identical, then it is not uncommon for the authorisation hold not to be released

In this instance, the people to contact to resolve are the bank rather than Hertz