Zephaniah attended the Paulinum Seminary at Otjimbingwe (1968–1971). He was ordained as a minister of the Evangelical Lutheran Church in Namibia in 1972, and taught at the Paulinum Seminary from 1973, and was principal 1976-77.
In 1975, Kameeta founded the Namibia National Convention, and was detained under the Terrorism Act while addressing an NNC meeting in Katutura, Windhoek to protest against the Turnhalle Constitutional Conference. He was kept in darkness and solitary confinement for a fortnight.
He was a parish minister in Lǔderitz from 1978 to 1981. He was elected vice-president of the Evangelical Lutheran Church in 1982 and deputy bishop in 1985. He was an exponent of Black Theology.
When Namibia became independent he was elected as a South West Africa People's Organization member of the National Assembly. He became its first Deputy Speaker. Between 2002 and 2013 Kameeta was bishop of the Evangelical Lutheran Church in the Republic of Namibia (ELCRN).
On Heroes' Day 2014 he was conferred the Most Brilliant Order of the Sun, First Class.