Here something a bit technical. I saw that robin's "From the Apocalypse" mod had a zombie unit without the chryssalid spawn animation. I made something similar for the TFTD zombie. You will have to set the deathframes in the armor section to 3 to make it work. Thanks to robin for the good idea!
If you ask yourself what this is good for: It will allow you to change the zombie into a non spawning-unit for e.g. a zombie-race-mod, where zombies kill humans and produce other zombies BUT no tentaculats. This could be acchieved before by removing the spawnunit entry, BUT then the dying zombie had no death-animation, which looked strange.
One more thing: If you remove the spawning from the zombie unit, you have to give it a corpse e.g. the male civilian corpse. In the rul-files a zombie_corpse is called for, but there exists none (as it was never needed due to the chryssalid/tentaculat spawning). If you forget that the game will crash once a zombie dies.
Oh well, as i said, it's a bit technical. But I am sure there are people outthere that do not want Tentaculats/Chryssalids to spawn and instead go for a zombie-only battle.
This actually would be a nice addon-mission: Relieve the city under attack from zombies....