In Callville Bay, killing young cazadores with long-fuse dynamite does not count towards the achievement.
To the south of Jacobstown and in Silver Peak Mine, killing young cazadores with tin grenades does not count towards the achievement.
The Southern Nevada Wind Farm (and the cliffside nest to the north) is one of the easiest locations to work at for this challenge. Because of the open and craggy landscape, it is easy to bait the cazadores away from the group, cripple their wings and then kite them around rocks while chucking explosives.
When doing this challenge in The Thorn, there is the possibility of hitting the guards or Red Lucy with the blast. They will then either turn hostile towards you or the cazadores.
This challenge is not repeatable.
It appears that young cazadores are immune to time bombs and can be immune to tin grenades. Sometimes they are completely unharmed when the adults are killed in the same proximity.[verified]
Adult cazadores may be immune to damage from a tin grenade.[verified]
In the Silver Peak Mine, sneak-attack killing cazadores with long-fuse dynamite does not count towards the achievement.[verified]
As long as the weapon you currently have out is a tin grenade, long-fuse dynamite or a time bomb, the kill counts towards the challenge. (Example- You throw a plasma grenade into a crowd of cazadores, and switch your current weapon to a long-fuse dynamite before the plasma grenade explodes; if the plasma grenade kills any of the cazadores while you have a long-fuse out, it'll still count towards the challenge. Note: Young cazadores still appear to be immune to damage in this instance, despite attacks coming from frag grenades, detonate plasma mines and plasma grenades that damaged nearby cazadores)[verified]
The above bug also works the other way around. When killing a cazador with a tin grenade or long-fused dynamite, it does not count towards the challenge if you switch to another weapon before the explosion. This is also true if you threw your last Explosive, since you are then unarmed. [verified]