whats the best way to get from zurich to interlaken and how far is it
Check schedules at the Swiss Rail site: http://rail.ch Journey time is just under 2 hours and requires a change in Bern.
A slower more scenic route is via Luzern and the Golden Pass train.
The Lucerne Route is much more scenic and not much longer really, I would suggest this way if you can spare a few extra minutes.
The scenic route via Luzern is more than just a "few minutes" longer. In fact, it's exactly an hour longer.