A year long loan deal had been agreed between Chelsea and Boro for the Dutch international but the winger found the lure of Paris too hard to turn down.
Agent Barry Silkman, who brokered the Riverside loan deal, has criticised Zenden claiming a move within the Premiership would have given him a better chance to prove his worth to Chelsea manager Claudio Ranieri.
"I think he has made a mistake, if a team is good enough for Mendieta, it is good enough for Zenden," he said.
Boro have missed out on another transfer target as Real Madrid midfielder Pedro Munitis has joined Deportive La Coruna, despite interest from Steve McClaren.