Moussa Konate opened the scoring with the help of a header from a Bakaye Dibassy cross in the 29th minute for Amiens.
Zungu then gave his side their second goal with a stunning finish from a distance.
The Bafana midfielder received the ball just outside the penalty area and curled the ball past the Metz goalkeeper to open his account in Ligue 1.
Zungu dedicated his goal to the victims of slavery in Libya.
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