Who carries out investigation for election-related criminal offenses?

Electoral Act 2006, 3

TheAnti-Corruption Commission shall investigate and prosecute any corrupt practicecommitted under this Act in accordance with the Anti-Corruption Commission Act.

(6) TheZambia Police Force shall enforce law and order at a polling station andundertake any criminal proceedings, subject to subsection (2), in respect ofany offence committed by any person in contravention of this Act or anyregulations issued under this Act.

http://aceproject.org/regions-en/eisa/ZM/Electoral%20%20Act%202006.pdf