Note: This route description includes a trip over UN13,660.
At South Zapata Lake, walk up an embankment on the east side covered with tundra and head into the basin SE of the lake on tundra, rock and snow earlier season. Swing gradually east then NE and follow a shallow couloir at about 12,600 feet to the ridge above. Most of this route will be over large, broken, but fairly stable rock. Intersect the ridgeline and head north over UN13,660, walking along a narrow crest with spectacular views on either side.
From the summit of UN13,660, head east along the ridge to UN13,577. Along the 400 foot drop, you'll encounter large, broken rock fragments that will slow your progress. Once at the saddle, the ascent will come easily on mostly smaller, broken rock.
If contemplating a hike over to California Peak, the connecting ridge north will go easily with one unranked, unnamed sub-summit along the way.
For descent, return to UN13,660, walk south along the ridge for a short distance and choose a couloir that drops back down to Zapata Lake. If filled with snow, this can be a very rapid descent. If not, it will be more of n unstable, talus descent.