Kariobangi Sharks forward Sydney Lokale scored four goals before Austin Otieno netted a fifth for coach Stanely Okumbi's team, to secure a 5-0 win.
Lokale scored the first goal in the 33rd minute after the Rising Stars had dominated the match for the first half-hour. The dominance forced Zanzibar to make a first change in the 25th minute when Abubaker Zaid took Yusuf Hassan's place.
Lokale added the second goal of the match in the 38th minute to give Kenya's team a healthy lead before the half-time break.
The youngster was to run riot again in the 78th and the 80th minutes as he stretched Rising Stars' lead beyond Zanzibar's reach. His third goal came from a penalty.
The fifth goal was scored by Ochieng in the 83rd minute.
Meanwhile, Tanzania crushed Ethiopia 4-0 in the other group match. Andrew Albert Chimsanga was the hero for the Taifa Stars juniors as he netted a hat-trick. Pius John Kelvin scored the first goal before opening the gates for Chimsanga.
Kelvin scored his goal in the 17th minute and Chimsanga got his first in the 37th minute. Chimsanga's second goal came in the 49th minute before the third one in the 84th minute.
The second matches for group stages will be played on September 24 with Kenya facing Tanzania while Ethiopia will entertain Zanzibar.
The last preliminary matches will be played on September 26 before the quarter-finals commence three days later. The semi-finals will be staged on October 2 before the penultimate action on October 5.