The first half of the Dzongri La trek is a long climb, and the way it is paced is what makes the top days comfortable. Here is the profile, stage by stage.
Day 3: Yuksom to Tsokha
You start at the forest check-post at the edge of Yuksom (1,706 m) and enter Khangchendzonga National Park. The trail crosses about three rivers on bridges to Sachen (2,179 m), a small man-made clearing you walk through. After a major bridge over the Prek Chu you reach Bakhim (2,727 m), a clearing with your first view of the high country. The forest of rhododendron and magnolia continues to Tsokha (2,956 m), a Tibetan settlement, where you sleep. That is a gain of about 1,250 m in a day, so we keep the pace slow.
Day 4: Tsokha to Dzongri
This is the steepest day on the way up: about 10 km and 6 hours, with a gain of about 1,000 m. Wooden log steps climb through dense rhododendron and conifer forest to Phedang (3,500 m), a clearing that is the last forest on the route. From there the trail switches back over loose rock to Deorali Top (3,980 m), marked with prayer flags, and drops a little to the Dzongri meadows at 3,960 m. The switchbacks are hard on the knees and ankles, so we go carefully.
Why the order works
By the time you reach Dzongri you have spent a night in Yuksom, a night at Tsokha and then two at Dzongri, with the pass day in the middle. We do not hurry the climb, and we do not add more height than the itinerary has. The sleeping altitude stays at 3,960 m.
Coming down
Day 6 is a descent of about 12 km in around 5 hours, from Dzongri back by Deorali Top, Phedang and Tsokha to Bakhim (2,727 m). The air thickens as you drop, and the forest closes in again. On day 7 you walk about 11 km in 5 hours to Yuksom through Sachen, crossing the suspension bridges over the Prek Chu, and sign out at the park check-post.
The trek is rated moderate, but it asks for fit legs on both of the steep days. A few weeks of stairs and loaded walking before you come is the best preparation.