Jan 8, 2015 - 7:17 PM
Hi maciejjacek, and welcome to MySwissAlps!
The itinerary you mention is fine. It really depends on what's your main goal. For such a short stay you can indeed visit one or two towns at the most. You may cut down on traveling time a bit by not visiting Zermatt all the way in the south, but focusing on the Lucerne and/or Interlaken regions instead. The timetable allows you to check such traveling times.
You'll probably be making quite some long journeys anyway, so it's wise to look into a rail pass. A 4 day Swiss Travel Pass would be the most convenient option. Whether it's the cheapest solution as well, can only be told if your itinerary is fixed and if you make detailed calculations as explained here.
These pages will provide you with information on the towns/regions mentioned, including tips for day trips, excursions and hotels:
Mind that many cable cars and mountain trains will be closed in April for maintenace. Main attractions like Rigi, Schilthorn, Jungfraujoch and Gornergrat are accessible (nearly) all year though.
If you like scenic train journeys and travel between Lucerne and Interlaken (or further south), make sure to consider the Golden Pass. It's for free with a Swiss Travel Pass.