"Piotr Jerzy Krzyzowski of Poland has become the first and fastest person to climb both Mt. Lhotse and Mt. Everest without supplemental oxygen, completing the feat in an astounding 1 day, 23 hours, and 22 minutes.
Krzyzowski reached the summit of Mt. Lhotse, the world's fourth-highest mountain at 8,516 meters, at 2:38 pm on May 21. Just two days later, at 2:00 pm on May 23, he stood atop Mt. Everest, the highest peak at 8,848.86 meters.
This remarkable achievement was part of the Seven Summit Treks Everest-Lhotse Expedition. Krzyzowski's accomplishment is notable not only for the dual summits but also for the extraordinary conditions under which he climbed."
Link:
https://thehimalayantimes.com/nepal/piotr-jerzy-krzyzowski-sets-record-with-double-header-climb-of-lhotse-everest-without-supplemental-oxygen