You can drive up the Buffalo Pass Road (about 10 miles west of Walden on Highway 14 in Jackson County) with a sedan. It is a good road-I know because it was a reconstruction project of mine about 22 years ago and it is still in great shape. Cannot remember the name of the trailhead at the summit but it is a good spot to enter the Zirkels from the south. Did a 24 mile llama trek through there about 8 years ago. Great views and some really neat country. Pretty easy hiking as well. Not sure if they have ever fixed the west side of the road dropping down to Steamboat Springs - it was still rough as a cob 8 years ago. Just don't try and access before early July-we are having a heck of a (good) winter here with lots of snow and when we reconstructed the road there was always a drift that blocked access to the trailhead until early July.