I can't seem to find a lot of info on the internet regarding Germany and Mexico's relationship during the war. The Wikipedia article for the Zimmerman Telegram mentions Franz von Rintelen oversaw funding of $12 million to Victoriano Huerta in 1915 to start a war, but doesn't go into any detail at all.
So I wanted to know just how much effort did Germany put into starting a war between the US and Mexico prior to the Zimmerman Telegram? Also, did the Kaiser and the German commanders like Ludendorff or Hindenburg know about the telegram? And if so did they approve of it or the general idea of starting a second Mexican-American War?
AH has featured several notable threads on the Zimmerman Telegram in the past, and while there's always more to be said, you might like to review some of these while you wait for fresh responses to your query. In particular:
The reason America joined WW1 was because they intercepted a message from Germany to Mexico asking them to invade America. If Mexico received this, what was the likelihood of them invading, and if they did, how much of a problem would it have been for America?, led by u/MurphyBinkings, which contains links to several other relevant threads
Was the Zimmerman telegram really a scam plotted by the British to get the United States into World War One?, led by u/thefourthmaninaboat, which goes into the history of the German attempt to inveigle Mexico into the war in addition to dealing with the explicit query from the OP