Zurich - 4N/5D

First and foremost, don't stay in Zürich. Zürich is a nice city, definitely in the first division of prettiness; but, you don't go to Switzerland to see cities, you go to see mountains, lakes and snow.
Unless you need to stay in Zürich (for work?), as soon as you land get the first train from the airport to Luzern or the Berner Oberland (Mürren, Wengen, Grindelwald etc.) and spend your 4 days there.

If you are stuck in Zürich, of course look round the city. Then take a day trip to Luzern (1¼ hours by train) and then on to Engelberg and cable car to the summit of Titlis ( http://www.titlis.ch/en ) to get up close and personal with a (small) glacier.
Bern is a nice city for a day trip.

Vegetarian food is not a big problem. Every restaurant will have at least one option, often more. Look out for "Rösti", a local potato dish, served with an accompaniment which may be meat, but also could be "Spiegelei" (fried egg) or vegetables. Also "Nusslisalat", a small leafed salad. Italian restaurants are common.

Decades ago I used to enjoy a Swiss lunchtime dish called "Russische Eier" (Russian eggs), which was basically a salad plate based on a hard-boiled egg with a variety of vegetables--often potato salad, cucumbers or green beans, beets, etc. In Googling I see that the term is now sometimes applied to what looks like the stuffed-egg appetizer that we in the US usually call "deviled eggs".

We ate at tidbits restaurant in Lucern. We love it and are not vegetarians. Check out Trip Advisor for vegetarian restaurants in each city you visit.

It sounds as though this is a rewards booking and your 4 nights of accommodation are set in stone.
Day 1 - Arrive Zurich - 4 nights
Day 2 - Excursion to Luzern (50min by train)
Day 3 - Zurich sights
Day 4 - Excursion to Bern (55min by train)
Day 5 - Depart

Another possibility would be to use one of those days to make some sort of loop trip by train (possibly with a postbus leg somewhere along the way). It would mean all day basically sitting on trains, but it might give a better view of the Alpine vistas most folks go to Switzerland to see.

This looks like it would be pushing the outer limits of what one would want to do in March (with short daylight hours). I'm sure there are better options, because I'm not familiar with Swiss geography, but here's one possibility: Zurich - Chur - Bellinzona - Interlaken - Zurich.

I've had an occasional day in Switzerland even in late May or early June when it was so foggy one could hardly see anything out the window of the train. If that sort of weather rolls in, you've got a day that should be spent in a city. Bern's especially nice if you get rain, because the historic district has a lot of arcaded streets.

Thanks All !

If I buy Zurich Pass will it be allow for Luzen and Interlaken also ? Or I have to buy separate ticket for same .

Plz guide me..

Thanks and Reagards

Biopan, by "Zurich Pass", I assume you mean the "Zürichcard", details here: https://www.zuerich.com/en/visit/your-city-travel-pass
This is a standard city-transport-plus-entry-to-tourist-attractions card. It only covers Zürich city and suburbs. That would be good for the day you spend in Zürich, but not for other places.
For train times and prices, go to the SBB (Swiss Federal Railways) website: http://www.sbb.ch/en/home.html
That shows Zürich HB (mains station) to Luzern, two trains per hour, journey time 50 minutes, full fare CHF 26 per person each way.
Zürich HB to Interlaken (via Bern), one train per hour, time 1h55, full fare CHF 70.

There is a good round trip, Zürich - Luzern - Interlaken - Bern - and back to Zürich (or vice versa). The middle leg (Luzern-Interlaken) goes over the "Brünig pass railway" and is very scenic. See Swiss railways map here: https://www.swisspasses.com/railpass/overviewmap_en.pdf

We did a day trip from Bern to the Schilthorn. You could do this from Zurich. The train network is totally set up for such things and everything syncs together. If you have a pass you'll need to buy supplemental tickets past Interlaken, Rick's book explains it.

The thing to see in Switzerland is not the cities (which are fine) but the mountains! So get out into the countryside.