Any advice on routes from Heildelberg to Murren, we are driving and hoping to drive in less than 6 hours
You have two options, one direct route that's slightly less scenic, and one longer route with slightly better scenery. Easiest is to take the A5 south to Basel, and from there, the A2 in the direction of Bern, following the signs to Interlaken and Lauterbrunnen. A little more scenic but more round-about would be to head towards Stuttgart at Karlsruhe, from Stuttgart in the direction of Ulm, from there to Lindau on the Bodensee (stop here for lunch), swing aroung Bregentz, into Switzerland towards Zurich, to Luzern and from there to Interlaken.