The project isn't connected to Sony's The Mask of Zorro and The Legend of Zorro. Instead it will be adapted from Isabel Allende's 2005 novel. Here's a description of the book from the author's official website.
A swashbuckling adventure story, Zorro reveals the history behind the legendary masked man.
Born in Southern California in the late eighteenth century, Diego de la Vega is a child of two worlds. His father is an aristocratic Spanish military man turned landowner, his mother a Shoshone warrior. From his father, Diego receives lessons in the art of fencing and in cattle branding; from his maternal grandmother, White Owl, he learns the ways of her tribe. As a child he also witnesses the brutal injustices dealt Native Americans by European settlers and begins to feel the inner conflict of his dual heritage.
At the age of sixteen, Diego is sent to Barcelona to be educated. Spain is chafing under the corruption of Napoleonic rule, and Diego, following the example of his celebrated fencing master, joins La Justicia, a secret underground resistance movement devoted to helping the powerless and the poor. With this tumultuous period as a backdrop, Diego falls in love, saves the persecuted, and confronts a great rival who emerges from the world of privilege. After many adventures-duels at dawn, fierce battles with pirates at sea, and daring rescues-Diego de la Vega, a.k.a. Zorro, returns to America to reclaim the hacienda where he was raised and to seek justice for all who cannot fight for it themselves."