You will get this during act 2 (After dealing with "The belgian problem" mission, the game gives you four missions and lets you choose your own way. If you do all of Zimos missions, he'll eventually give you this mission (with the same name on the phone screen).
Once you beat that mission this trophy will pop.
There's not a lot of challenge to the mission but there is a really useful minigun the game points out, grabbing it and hanging on to it, can make the game far easier if you don't have a rocket launcher (if you do, the rocket launcher can be slightly easier to use than the mini gun)