You're allowed a stopover, a destination and an open jaw.
I flew JFK-GRU (destination), GRU-JFK (stop over), and JFK-LAS (open jaw) all low in BE/F. I tagged the las segment on for free!
BUE=EZE? If you're flying to EZE and connecting in less than 24 hours to mvd, then you won't have a stop-over and will be allowed to have one at your origin. If youre spending more than 24 hours in EZE, that will eat your stopover and you'll be out of luck.