Rabbi Zvi Yehuda on The Sefarim Blog: https://seforimblog.com/2021/04/response-to-criticism-part-4-rabbi-zvi-yehuda-and-the-hazon-ish/

Torah in Motion: https://torahinmotion.org/speakers/rabbi-dr-zvi-a-yehuda 

Torah Musings: https://www.torahmusings.com/2007/05/r-zvi-yehuda-on-chazon-ish/

In the mid-1940s, Zvi joined his father Jacob Jehuda, at a visit with the Hazon Ish. The Hazon Ish conversed with the young Zv'aryeh and invited him to study together. He was impressed with his critical thinking skills. Hazon Ish had no children; yet had a small group of young students for whom he was like a father/mentor figure. During this time, Jabob Jehuda was very involved in work as an architect and artist (he had participated in the 1939 World's Fair displaying his work on Solomon's Temple), and it worked out well that young Zvi would stay with the Hazon Ish, help him around the house, and study with him daily. Hazon Ish also asked that Zvi accompany him during visits to yeshivot and during certain meetings where he felt it was important to have another person in the room to capture the conversation and comment on the discussion. They developed a close connection.

The Hazon Ish passed away in 1953, while Zvi had enlisted in the IDF. Quite the passivist and academic by nature, Zvi was not a combat soldier but was assigned to the army educational division. During their years together and afterward, they wrote to each other, and Zvi kept the letters all his life. Some were published in the קובץ אגרות חזון איש (the publisher removed the names of letter recipients). After Rabbi Yehuda's passing, the Yehuda family donated the letters Zvi carefully saved to the National Archives of Israel where they remain on display in the National Library.