Can we get a link to download the mod and a test save to debug the issues?
No, there is no classic ruleset attribute for that, zombies always spawn as hostile.
I see there is a Y-script method to be able to change the zombie faction, but I don't think it is usable in this context... maybe Yankes can clarify.
The game doesn't crash. With the help of Skyhawk, it was managed to make the new Chryssalid created after the zombie's death be friendly in addition to the "spawnUnit:" command. The zombie will be friendly by default. It is true that the Chrysalid created after the zombie's death will lose its ability to control the mind or cause panic, because it will be of the "Unit" category and not of the "Soldier" category, and the ability to use the weapon built into the armor will be taken away. Also thanks to Skyhawk, as soon as the new unit is created, it can be used immediately, and you don't have to wait for the next turn. In any case, I am attaching a zip file, you don't need a saved game, any impromptu battle will do, but according to the basic rules of the mode, it is mandatory that the battle be on land, because the Chrysalid cannot exist underwater, its weaponry does not work. I would have liked not only the weapon to be unusable underwater, but also the unit itself to become completely unusable underwater, but this is one of those things that I couldn't solve. In addition, there are no projectile animations, and there are no stun gun animations either, the sounds have not been put back in yet, I haven't gotten there yet, but the sounds are finally there. This will work roughly the way I want it to. But it would be nice if there was a way to prevent the tank from becoming a zombie, and all other weapons would be destroyed immediately, regardless of the strength of the armor, and only 1 zombie would be created instead. However, there is one exception, armor that is specially developed against Chryssalid attacks, it is immune to it from the start and works well.