I followed your advice but I have this error at launch
entitygroup :
<configs>
<append xpath="/entity_groups">
<entitygroups>
<entitygroup name="ZombiesAll">
<entity name="zombieBoe"/>
<entity name="zombieJoe"/>
<entity name="zombieSteve"/>
<entity name="zombieMoe"/>
<entity name="zombieYo"/>
<entity name="zombieBusinessMan"/>
<entity name="zombieArlene"/>
<entity name="zombieDarlene"/>
<entity name="zombieMarlene"/>
<entity name="zombieSkateboarder"/>
<entity name="zombieCheerleader" prob="0.3"/>
<entity name="zombieOldTimer" prob="0.3"/>
<entity name="zombieBiker" prob="0.3"/>
<entity name="zombieFarmer" prob="0.3"/>
<entity name="zombieStripper" prob="0.3"/>
<entity name="zombieUtilityWorker" prob="0.3"/>
<entity name="zombieNurse" prob="0.3"/>
<entity name="zombieSteveCrawler"/>
<entity name="zombieFatHawaiian" prob="0.3"/>
<entity name="zombieBehemoth" prob="0.1"/>
</entitygroup>
</entitygroups>
</append>
</configs>
entityclass :
<configs>
<append xpath="/entity_class">
<property name="zombieBehemoth" extends="zombieTemplateMale">
<property name="Prefab" value="NPC4m"/>
<property name="SoundRandom" value="Enemies/Base_Zombie_Male2/zombiemale2roam"/>
<property name="SoundAlert" value="Enemies/Base_Zombie_Male2/zombiemale2alert"/>
<property name="SoundAttack" value="Enemies/Base_Zombie_Male2/zombiemale2attack"/>
<property name="SoundHurt" value="Enemies/Base_Zombie_Male2/zombiemale2pain"/>
<property name="SoundDeath" value="Enemies/Base_Zombie_Male2/zombiemale2death"/>
<property name="SoundSense" value="Enemies/Base_Zombie_Male2/zombiemale2sense"/>
<property name="Mesh" value="Monsters/Behemoth/BehemothRagdoll"/>
<property name="AvatarController" value="AvatarZombie01Controller"/>
<property name="ModelType" value="Standard"/>
<property name="WalkType" value="9"/>
<property name="ExperienceGain" value="8982"/>
<property name="MaxHealth" value="5000"/>
<property name="DeadBodyHitPoints" value="700"/>
<property name="PhysicsBody" value="zombieStandardFemale"/>
<property name="RootMotion" value="true"/>
<property name="HasDeathAnim" value="true"/>
<property name="ReplaceMaterial1" value="entities/zombies/materials/Z_eye1"/>
<property name="HandItem" value="meleeHandZombieBehemoth"/>
</append>
</configs>