Its best to park at one of the free parkingspots in Zierikzee, the one nearest by is the big new parkingspot called Havenpoort (4301 RN) , after parking you pass the drawbridge to the center of Zierikzee, the second big one is at the Hoofdpoortstraat (4301 AT)(close to the mill and the harbour), if you pick the last one you can make a nice stroll for Max. 7 min. Through the Nieuwe Boogerdstraat/Visstraat, that street ends at the Havenplein only a few seconds from De Theetap.
Have a good trip and see you soon!