At Zwolle Station take the train to Dalen Station. From here it's a 25 minute walk to the park.
You can also take the train to Coevorden Station, where you can take a taxi to De Huttenheugte.
(Taxi GTL Kuiper 0591-855435)
The closest airports to the parks are Amsterdam Schiphol (NL, 129 km) and Bremen City Airport (DE, 207 km).