The Hertz desk will just advise you if they have a NL car in MUC that needs a transfer, it cannot be booked ahead. If they do have a car available to want to get back to NL, you pay the regular rate(s) but no one-way surcharge.

A friend of mine once explored the options to drive from MUC to France that way on short notice. Sadly they never had FR cars in MUC when he called. As you can see on the Hertz site, they mostly have cars from IT in Munich.