Why Did Germany want Mexico to join them in WWI?

Why did the Zimmerman telegram finally persuade the US to go to war with Germany?

Zimmermann sent the telegram in anticipation of resumption of unrestricted submarine warfare, an act the German government expected would likely lead to war with the U. S. Zimmermann hoped tensions with Mexico would slow shipments of supplies, munitions, and troops to the Allies if the U. S. was tied down on its southern