Indeed this stallion is listed in "Longevity of Mammals in Captivity" (Weigl; 2005) as holding the longevity record for a Chapman's zebra. According to this book, he arrived at Marwell on 12th January 1970 and was sent to Whipsnade on 18th July 1991 where was was still alive on 12th August 2004 at an estimated age of thirty-six. And he lived for some years after this.
I saw a single Chapman's stallion at Whipsnade on more than one occassion before I discovered he was the original Marwell one, now retired from their group. Even into his thirties this male was still in top condition.