It should work, the default 0.01 value "Resistance_to_Explosions" in PvZmoD_CustomisableZombies_Characteristics.xml should do the work.

With which zombies did you try?
Some of them are more resistant.

When you press numpad4 you don't need to restart the server but it can take 30 seconds to refresh already spawned zombies characteristics.

You can lower this timer to 1 second by setting the "Debug_Mod" value to 1 in PvZmoD_CustomisableZombies_Globals.xml
Just don't forget to set it back to 0 when you finished your tests because debugmod is a little bit more server resource consuming.

i replaced all Resistance_to_Explosions to 0 and to 1 the whole file but i can not kill them with HEs :D or it needs 5 of them i will try and tell u if a zomb will generally die of it.
normally 1 HE should be enough to kill a whole pack of them right?

i made a quick vid 4 u. The settings in the file are the defaults 0.01. I could see that the non-military zombs died on first HE. The milis diddn´t even on the 2nd or 3rd.

https://www.youtube.com/watch?v=bExLU9gdqbc

any advice?

Oops I thought I answered to you.
Can you send me a zip of your custom zombies profile folder on discord Liven#0879 pls?

ok, got it fixed! I have just overseen the Resistance_to_Explosions for some zomb classes. After adjusting them as well, the damage of explosives was like expected. Thank u Liven for ur time and help.