"This is the greatest day of my life for one reason only, because people believe in me," the 60-year-old de Villiers said in Zimbabwe.
The arrival of a former Springboks coach is a big moment for Zimbabwe, but it also marks a return for de Villiers after the criticism he received while coaching South Africa appeared to have stunted his career.
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His tendency to make controversial comments didn't help. He once accused New Zealand's team of cheating and appearing to defend one of his players for eye- gouging.
De Villiers' appointment was described as "a statement of intent" by Zimbabwe Rugby Union president Aaron Jani.
"No one will ever wave the magic wand for us to become a force in world rugby," Jani said.
"It is up to us as a team and as country to start believing in ourselves."
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Zimbabwe must finish in the top two in the Africa Cup competition later this year to have a chance of qualifying for the 2019 Rugby World Cup in Japan. If they win the tournament they qualify automatically. If they finish second, they get another shot at the World Cup through a play-off.
"I can't promise we will win everything," de Villiers said. "The only promise is that we will prepare, not only prepare, but we will be ready."