Here's a description of each assassination.
Eagle Strike and assassinate: I couldn't do a double eagle strike because the programming is different for one of the targets, and he can't be air assassinated. I lure the targets into place and use the super/hyperblend exploit to remain undetected. After I air assassinate the first target I regularly assassinate the second.
Hidden gun from far distance: The mission will fail if either target gets 50 meters away after detecting you. I kill the first with throwing knives, then lock on the second with the hidden gun. He's about 48 or 49 meters away when I shoot him.
Double stunt: I lure both targets into place, jump from a building, roll, and double assassinate. The targets have to be lured since they are too far from each other to double assassinate while they are walking.
Haystack assassination and regular: I do a hidden assassination on one of the targets while he walks past. You are unable to do a hidden assassination on the second due to a programming error, so I just run up and do a regular assassination before he can run away.
Hiding in plain sight: I take advantage of an exploit to set up the targets for a double assassination. One of the targets won't detect you at all unless the other detects you. The other won't detect you if you are behind him.