too much for 2 weeks?

That's not to much if you limit your hotel stays to 3 over 2 weeks.

What do you want to see in Belgium?
What do you want to see in Normandy
and in Holland?
Will you use a car in Normandy?

It would be too much for us, but not for everyone. What are your expectations for each place? Give serious thought to what you actually want to see and do.

It would be for me but I prefer slower pace/fewer places instead of racing from place to place.

We did that exact trip in 2010, in 14 days NOT including arrival and departure days.

We only spent 1 night in Brussels though.

If you haven’t been to Paris and Amsterdam before, then I think you have one stop too many, so I would drop Belgium, as you aren’t going to see much of the country in your timescale. Take the train between Paris and Amsterdam.

Do you have 2 full weeks on the ground? If you are going to lose a day at each end in transit, then I would consider just visiting Paris and Amsterdam with a day trip from each to explore somewhere of interest to you.

We did this trip a few years ago. We started in London, took the train to Brussels, then trained to Amsterdam. When we finished in Amsterdam, we took a train to Lille, which is in the north of France and rented a car to drive along the coast to Normandy and a bit of Brittany (St Malo). We based ourselves in Bayeux and also spent one night at Mont St Michele. We then drove to Paris, dropped our car off at Orly airport and then took a cab into Paris. We flew home from Paris at the end of the trip. We did this in a little over 2 weeks. You can also follow this itinerary in reverse. Have fun planning!

Why these 4? Have you been to any of these before?

I get the feeling that since you posed the question, you are already thinking it is too much.

You are proposing 2 locations a week, minus travel from one place to another. Do more research regarding traveling from one place to another, that will help you decide if your itinerary is too ambitious.

We've been to Brussels, Paris and Amsterdam. If you'd asked me 15 years ago, I would probably answered it is not too much. We have changed our travel strategy recently. We spent 10 days in Tuscany, staying the entire time at one agriturismo. We went to Loches France and London last May. We spent a week in each location. Slowing down has been refreshing.

Unless there is a personal connection with Normandy and Belgium, I'd recommend just Paris and Amsterdam.

I understand some saying it's too much. We've slowed down and now spend more time in each place, but we've retired. When working, we tried to get to as many places as possible, simply so that we'd know where we wanted to go back to spend more time--and we generally only had 10 days, not 2 weeks! I think it is fine---Amsterdam can be done (IMHO) i 1 or 2 nites (2 days). Paris is where you'd probably want to spend the most time. In Belgium, we flew into Brussels (you could do that in one day), took the train to Bruges, and got off in Ghent for the day. Really loved Bruges. I would do it! Then you can decide where you want to return for more time.