This is how you load the zombie in the level:

you = ent_create("zombiek.mdl",vector(530,106,-47), zombie_fight_against_eachotherr);


It is the same with the player:

you = ent_create("zombiek.mdl",vector(530,106,-47), character_walking);


Did you have a look into the manual?
Index 'ent_create'.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt