The correct answer is: "Mexico would get Texas, Arizona, and New Mexico"
Arthur Zimmerman (1864-1940) was the State Secretary for Foreign Affairs of the German Empire during 1916 and 17. He is mostly known because of the secret communication he sent to Mexico during WWI, in January of 1917, called the Zimmerman Telegram.
He aimed to propose and alliance between Germany and Mexico, as a measure of prevention in case the United States decided to join the war. The proposal offered to Mexico that they would recover their former territories of Texas, Arizona and New Mexico.
The communication was intercepted by the British intelligence bodies, and caused the opposite effects to the desired ones. It enraged the US, that ended up declaring the war to Germany in April 1917.