Hello Grace6341,
If you are based in Voorburg and going more south-west I think it’s best to rent a car. The traffic jams around the larger cities like The Hague, Delft and Rotterdam will give delay, but become irrelevant once driving through the province of Zeeland.
I suggest the following route: Head to Spijkenisse/Hellevoetsluis via Rotterdam (Benelux tunnel). Drive over the Haringvlietdam (part of the “Deltawerken”) and have a first stop in Goedereede. Tiny, cute, ideal for a coffeebreak and it’s easy to park your car there free.
Continue your itinerary via the Brouwersdam and then you actually enter the province of Zeeland. Going further south you will drive over the first two sections of the Storm surge barrier. Very impressive, especially when you know that the main part is under water. To understand what make The Netherlands so Dutch, you need to visit the Delta Expo on Neeltje Jans (clearly signposted).
Going further to Middelburg you drive over the third and last section of the barrier. Not to be missed is Veere, a tiny harbour with it’s still dominating church and gothic style town hall. Free car park alongside the canal, east of the city centre.
Middelburg is nice with it’s laidback atmosphere and with it’s also gothic style (former) town hall. It now houses the Roosevelt Academy, named after F.D. Roosevelt, because the families origin is based in this province. Further the abbey and the old harbour (what else) is beautiful. Climbe the “Lange Jan”, the abbies bell tower that still during centuries dominates the skyline of the city, from there a fantastic view over the peninsula of Walcheren if the weather co-operates.
You can drive back to Voorburg via Goes, via the 5km long Zeelandbrug and Zierikzee. Even Goes has an nice market-square, rococo style town hall and old harbour, but I think it’s better to go directly to Zierikzee. Just to avoid a possible overload of your schedule. Arrived there, according to me the best place to park the car is just south of the Zuidhavenpoort and then to walk over the old bridge into the old city centre. Zierikzee is also a good place for having diner, before going back to your base in Voorburg and good for avoiding the traffic jams. Car parking is free after 18.00h.
As it is still the shoulder season, the wheather can be very pleasant and Zeeland surprisingly quiet compaired to the densily populated and bustling other parts of The Netherlands. As it is also a wind-swept area, no surprise there are a lot of old-fashioned windmills, still in good shape in many villages.
Other places within easy reach from Voorburg are the windmills of Kinderdijk, about 20km east of Rotterdam. And also the castle of Haarzuilens near Utrecht. Have no idea if these places are accessible by public transport, check that first.
As you can see there is a lot to do, so enjoy your planning, enjoy your stay.
Wilco3