What faction is she in? Fringe or Separatist?

She looks good, but one thing concerns me: Changeling is very, very powerful. You can calmly walk her right up to an enemy commander or other important tech piece, and your opponent can do nothing about it. She would also be insanely powerful in a swap squad, because she's an invincible swapper (like a super-Diplomat, who can go on solo missions).

Maybe re-working the ability to require your opponent to roll a save of 16 in order to attack her when Changeling is in effect or something. Or maybe make it so that Changeling only works as long as Zam is on your own half of the map.

I would suggest something like: If an enemy character does not have LOS to this character at the start of her turn then this character may not be attacked until the start of the next round.

Personally, I like this version the best. It makes her valuable as a swap piece, but not overpowered. She would re-gain the benefits of Changeling after she was swapped out each time (assuming she's swapped out of LOS), which is an interesting mechanic.

However, I could see Rebel and NR squads abusing the ability by giving her Mobile Attack. She starts her turn out of LOS, she steps out and shoots something (with Accurate), and then she moves back out of LOS...even if you can reach her that round, she still can't be attacked. That's a pretty sweet use of 25 pts.

Changeling (If an enemy character does not have LOS to this character at the start of their turn then this character may not be targeted until the start of the next turn.)

That is an interesting take. So if the attacking character does not have LOS to the changeling character when they activate they can not attack them. That still has the Mobile attack problem though.