Zugspitze and Neuschwanstein in one day???

I guess having a car would make Munich-Zugspitze-Füssen-Munich in one day more achievable, but I have to ask why? Doing it with an overnight stopover would be less hectic, and you would be able to see more places and give the places more quality time. Going by car in one day would be tight; doing with public trainsportation in two days would by less expensive and less stressful.

There are a number of buses from Garmisch-Partenkirchen to Füssen each day. You could go to Füssen for the night, see the castles the next morning, and return to Munich the next night.

Or, my choice would be to spend the night in Oberammergau, see that cute little town, then go to Füssen the next morning. Here is where I would stay in Oberammergau. It's reasonably priced, near the bus station, and Frau Richter speaks good English.

It is feasible, but weather could ruin your plans. It's not worth ascending Zugspitze if the summit is enveloped in fog. Enjoyment of Neuschwanstein, on the other hand, depends far less on the weather.

If you decide to try this combo excursion, don't try to schedule it too far in advanced. Check the short-term weather forecast when you arrive, and pick the day that gives you the best conditions.

I think even in summer with the most daylight this is too much. No time to enjoy yourself or the places you are visiting. If it's your only chance to visit these places than go for it, but take the rental car with a good navigation device. Even then I think it would be a tight. The Zupspitz Gondel and not the train and early to avoid the crowds? Tickets purchased in advance for a specific time at Neuschwanstein to see the inside of the castle?

Thanks everyone! Some great advice here :) I think we're going to build in an overnight stop near this area so we can enjoy our time and not be too rushed, but also not waste too much time going to and from Munich. Thanks!!!