Itinerary help: Arrive Amsterdam Dec 12, depart Zurich Jan 9; 2 middle aged adults

Never done Europe in the winter. Hopefully those that have can help you here, I would suggest to button down your lodging around Xmas and New Years asap. Don't forget food shopping in advance of those days for in room meals.

Delft is a nice place, probably fits your style of travel well. Antwerp too.

...not knowing where to go in Germany

19-22 / 4 nights in Germany: Not a lot of time. I wish I had better things to say about Cologne as a base for your time. I think of it more as a 1-day kind of place. Aachen is lovely and makes for a nice stopover. On the whole I think you need to see some additional towns for a better picture of Germany. I'd suggest this (rail times are just examples.)

• 19: Train to Aachen (9:40 - 11:36) for stopover. Train from Aachen to Koblenz (15:51 - 17:46.) (A similar stopover in Cologne would be doable as well, perhaps for 2 additional hours?, if you choose not to visit Aachen. )

Koblenz itself has a scenic setting where the Rhine and Mosel rivers meet and a small but nice old-town center. But its main advantage is its role as a rail hub for seeing nearby places. It's a good choice in the winter months.

• 20-22: Day outings could include your choice of these places; approx. 1-way travel time is noted. Each destination involves a scenic river-valley train ride.

Cologne (1 hr.)
Limburg (half-timbered old-world town, 1 hr. via the Lahn River)
Trier (outpost of ancient Rome, 1.3 hrs. via the Mosel River)
Mainz (1 hr. via the Rhine Valley)
Braubach (10 min. from Koblenz on the Rhine) / Marksburg Castle ( open for tours 11-4, walk of 25 min from Braubach station or taxi)

You could indeed make a stopover in Heidelberg on the way to Strasbourg. Good choice.

I'm sure you have reasons for visiting Lyon. But as a way of streamlining your trip I could easily see leaving it out and traveling from Strasbourg to Zurich via Stuttgart (Esslingen and Tübingen are interesting, attractive places near Stuttgart.)

My 3 cents:
Cologne: Stop into Papa Joes Biersalon. Decent food, Koelsch beer, great collection of antique musical automatons plus a modern one "Tuenis & Schael". http://www.papajoes.de/about-papa-joes/
Check their Facebook page next month to see their live music schedule for December. Always interesting.

Strasbourg to Lyon: There are several direct TGV's every day. Book now for inexpensive tickets and inexpensive upgrade to 1st class.

Dec 31 to Jan 2: See where the best New Years Eve festivities are in Geneva, Lausanne, Montreux. Pick one for these 2 days. Train from Lyon to Geneva is a TER, so no need to buy in advance, always the same price, unless you get a senior discount.

Jan 2: Take one of the Golden Pass trains to Interlaken, then train to one of the Berner Oberland towns like Wengen or Muerren. I know your schedule says Jan 1, but that is a Saturday, and on Sunday Jan 2 all the holiday skiers will be leaving town and hotel availability is likely to be a lot better.

Jan 6: Train to Luzern and stay for the rest of your trip. It is only 1 1/4 hour to Zurich Airport by direct train. If your flight is after 10 am, should be no problem.

I have been to all the places you mentioned except Antwerp.

Here is what I recommend:
1) Amsterdam, yes, minimum of three days there. Delft is good, but I loved going out to the Zyder Zee on a day trip.
2) Belgium, go to Brugges, forget Antwerp. Brussels is nothing special except the Grand Plaza. If you go there don't spend more than a day.

3) Cologne and Aachen are good if you go directly there from Amsterdam and skip Belgium. Cologne's cathedral is about the only thing you want to see there. Aachen is small and half a day is good.
4) Forget Bonn and Mainz and go to Heidelburg. There are some great Rhine River short cruises between Cologne and Frankfurt, but not sure they go in the Winter.
5) A day in Heidelburg then on to Strassbourg, which is great.Two days should be enough for that city.
6) Suggest choosing between Lyon and more in Provence, France OR head to Switzerland. Since you have Swiss ancestry you probably want to go there.

7) Switzerland, lots of great choices, but take are, you are going there in Winter and it snows a lot there. If you drive, you may have issues with ice and snow. Many places to see, I recommend going to Interlakken. Consider Lucern as well. One day in Zurich.

Thank you so much to all who’ve contributed already! I really appreciate you sharing your time and expertise.

(I feel compelled to add: we actually booked award flights to Japan all the way back in February. Seemed like a safe bet at the time. Can’t believe it’s still completely closed to tourists. But that is the reason for this relatively last minute travel.)

Russ, a little embarrassed to admit that besides being geographically convenient for our arrival and departure cities, part of the reason for selecting Cologne is Anthony Bordain’s fondness for it. We also like places with welcoming and open people with a good sense of humor and a fondness for drink and conversation. Glasgow remains absolute tops in my book for this (most conversation with locals we’ve ever had, though it takes a few half pints before I work up to about 80% comprehension ;) ), but Porto was a close second. This is obviously not a tour of Germany and I’m totally fine with that, but it’s right there so I'd like to get a little taste. Your recommendations are great. Checking them out asap.

Sam, "antique musical automatons" is right up our alley! Hubs is a mechanical engineer and a musician. I can't skip this in good conscience now that I know it exists. ;-) Your Switzerland suggestions are very helpful. I was getting overwhelmed and completely puttered out for planning that last week. I got a second wind last night though and started looking at the Glacier Express. Even if we don't do that, I'm getting a little more pumped about Switzerland, even in the winter (will not be driving!). Gotta dive in to the digital guidebooks I got from the library.

Geovagriffith, you are right that doing Lyon AND Switzerland is probably the monkey wrench. I considered skipping Switzerland for more France but can't get us award flights out of Marseille, Nice, or even Paris. (Not willing to spend more than 30k miles, $100 absolute max in taxes/fees, one stop max.) Maybe I'll spend a little time looking for cheap flights with cash, but generally we're able to afford these long trips because we can spend that money on the ground instead of in the air. I studied French in high school and college. Can barely string together a sentence these days, but my unfulfilled adolescent Francophile dreams still pull me towards France.

I will search the Belgium boards because I'm curious what others think. I've heard Bruges can feel a little Disney like/only for tourists. I don't want to skip Belgium altogether when it's right there because we love beer, especially Belgian style beers, farmhouse ales, sours, etc.

Booking accommodations for the holiday weekends and any high speed train segments asap are the priority. Tourism is down so much that I'm finding no lack of choice for the rest of the trip, even this late in the year. Christmas in Strasbourg will be the toughest, I think, and I'd be willing to rearrange the itinerary if possible/necessary. I agree with multiple comments that "streamlining" is probably a good idea. But when you've got four weeks and it feels like everything's "right there!", it's so hard to narrow the scope.

Thanks again. This is all wonderful info.

Amsterdam 13-15, you might be ready for a day trip from Amsterdam because of the crowds.
I also suggest visiting the rooftop lounge at the DoubleTree by Hilton Amsterdam Centraal Station. The view is one of the best in Europe.
You can then depart the Amsterdam Centraal train station to the Antwerpen Centraal station and store your bags while you sight-see. You can then take a direct train to Bruges (1h 30m) and sleep there and take a day trip to Ghent (30-minutes).
You can visit Brussels the day you depart for Cologne and store your bags at the Bruxelles Midi station while you visit the Grand Place, etc. Bruges to Bruxelles Midi takes 1h and Bruxelles Midi to Köln Hbf (Cologne) takes 1h 45m.
A day trip from Cologne could be a direct train to St Goar (2h). Bacharach is another 15-minutes from St Goar. A direct train from Bacharach to Cologne (Köln Hbf) takes 2h 15m. To learn more purchase Rick Steves Germany guidebook.
A train from Köln Hbf to Bonn Hbf takes 30-minutes. A train from Bonn Hbf to Strasbourg requires two transfers, one in Siegburg and the other in Offenburg. The total time it would take is 3h 30m.
You can take a direct train from Cologne (Köln Hbf) to Heidelberg Hbf (3h) but continuing on to Strasbourg would make it a very long day, especially since you would need to change trains in Karlsruhe (30-minutes) and then it takes another 45-minutes to get to Strasbourg.
There is a direct train from Strasbourg to Lyon Part Dieu (4h). From Lyon Part Dieu you can take a direct train to Geneve (Geneva; 2h). Day trips include Lausanne, (45-minutes by direct train) and the Château de Chillon (requires a change in Montreux; 1h 15m).
You can then take a direct train from Geneva to Zurich HB (3h). A good day trip option is Bern (1h by direct train).

Agree with Russ about ... everything. He was very helpful when I planned our Germany trip a few years ago.
In Brussels there is a musical instrument museum that your husband might find fascinating. My husband is also a musician and loved it (even though we were jetlagged and a little hungover from business class libations, lol). We also loved Bruges. If you decide to go, PM me for a wonderful B&B.

Since hubs likes antique musical automatons, why not go to the king of all working automaton displays, the Speelklok Museum in Utrecht , which is truly spectacular - https://www.museumspeelklok.nl/lang/en/

You can then depart the Amsterdam Centraal train station to the Antwerpen Centraal station and store your bags while you sight-see. You can then take a direct train to Bruges (1h 30m)

Caroline, I just realized this direct evening train does not operate daily. I’m looking at Mon, Nov 8 that shows a direct train departing Antwerp on Deutsche Bahn early evening but not on Mon, Nov 1. You might want to consider sleeping in Brussels.

Thank you, everyone! I have to admit, our itinerary is still very much up in the air since Covid situations seem to be changing daily. I've made some reservations that can be cancelled for free until very late. I've gotten much more comfortable traveling on the fly in recent years, and that might be what ends up happening this time. Baahhhh.... just when you think this thing is somewhat under control it comes roaring back. We're both getting boosters next week and still planning to go, but I think being flexible might be key to enjoying it.