If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Zambia.
It is prohibited for any person with a liquor license, to sell, serve or supply alcohol beverages to anyone under 18 years of age. Before the Liquor Licensing Act was enacted in 2011, the minimum age to sell, serve and supply alcohol beverages was 14 years.
You can find more legal details and links here:
Wikipedia Legal Drinking Page