After a number of missed opportunities, Zoo finally broke the deadlock in the 45th minute when Castro Lihanda delivered a cross that was controlled by Tayo, whose effort was cleared, but the ball fellto Onchwari to slot home from a second rebound.
Vihiga United were unable to get an equaliser in the entirety of the second half as Zoo picked up maximum points for the first time in the ongoing campaign.
At Moi Stadium, Wazito were defeated 1-0 by Western Stima as the goal by Baron Oketch handed the Kisumu club the first-ever win over the Nairobi club.
Oketch scored in the 28th-minute and Francis Kimanzi made a change in the 37th minute when he withdrew Vincent Oburu for Michael Owino.