Willie Nelson SMOKES the Diaz Bros! (PHOTO)

Willie Nelson can take BOTH Diaz brothers at the same time ... at least when it comes to smoking weed.

The country music legend (and pot icon) was proudly displaying his new boxes of the new Nick and Nate Diaz line of marijuana cigarettes.

The company behind the pot products say "Nate's Energy" weed is a pre-workout blend and "Nick's Recovery" is to help athletes post-training.

Or, if you're Willie Nelson ... pre-show, post-show?