If you’re going for the Royal Demolitionist trophy, you can probably get this one at the same time.
During the APC encounter in chapter 6, just wait for the truck to spawn at the top of the stairs and throw some C4 at it. There should be 4 enemies in the truck, which is all you need for this trophy.
Just make sure to take out the APC first.
Defeat 4 enemies with one C4 detonation