Hlongwa, who is a graduate of the popular KZN Academy in Durban, joined Pirates last year and featured in their Multichoice Diski Challenge setup.
Zikalala was released by the Buccaneers before the start of the 2016/17 season, upon his return from a loan spell with Golden Arrows.
Davis, who joined the Mayfair-based outfit from the Nedbank Ke Yona draft in 2014, spent last season at Univesity of Pretoria after parting ways with his previous employers.
Kings finished eleventh in their debut First Division season after winning promotion in 2015.
The Magic Boys, who advanced to the semifinals of KZN Premier's Cup currently taking place in Richards Bay, after beating newly formed Richards Bay FC 3-1 on penalty shootouts on Saturday, have also signed Bonginkosi Dladla, Mzikayifani Ngidi, Steve Nzambe, Zothani Nzimande and former Arrows 'keeper Ricardo Goss.