Zheng returns to The Valley in a £2million deal following a successful loan spell last season.
"Returning to Charlton is not a bad choice," said Zheng, who had held discussions with Newcastle and Birmingham. "As a Chinese player, I have nothing to complain about because we have few choices.
He added: "It was a pity that I couldn't land a deal with a Premier League side. There were a lot of reasons.
"I can't decide my fate on my own. It couldn't be achieved unless all the parties including the English clubs, Shandong and me could reach a consensus."