Attack of the Zygons

[Shining_Finger]

This is a thread where we share ideas on how to beat Zygons. 
This is what a Zygon looks like in the flesh. 

And this is one way they could be hiding among us: 

If you haven't already guessed, this is a Shapeshifting Alien. If it keeps the victims alive, it can remember things in the victims memory at all times. 
If they have killed them or the victim is just dead, they can't remember these things, but they can remember things they have already remembered and they will continue to do their personal habits. 
They will keep ailments of the people they have shapeshifted into, such as Ashma. 

They can knock you out at short range if they shape shift into that first form with lightning from their hands. They do this only if they may wish to use the victim's body to their advantage, such as to shape shift into the victim. So they could still kill you while disguised as a human, through a gun or other means. 

Any ideas, anyone? Literally anyone could be a Zygon. 
Watch your back. 
My idea is to perpetuate that you are actually a Zygon, but this probably won't work in the long run.