I used a special script to have a zombie punch open a door, but didn't destroy it (would be rather easy to make that so, though).
One sec, lemme search my portable HD...
EDIT: Voila!
desc = Half-Life 2 Zombie Follow and Slash
;Original Script by Bond, Modified by Airslide
;Triggers
:state=0,waypointstate=0:animate=2,waypointstart
:state=0,waypointstate=3:animate=2,waypointnext
:state=0,waypointstate=4:animate=2,waypointrandom
:state=0,waypointstate=5:state=10
;:state=10:movefore=2,animate=2
:state=10,nearactivatable=0:settarget,activatetarget=3,setframe=92,state=3
:state=3:incframe=92
:state=3,frameatend=92:state=1
;Original Code>>>
:state=1,plrdistfurther=40:rotatetoplr,movefore=2,animate=2
;:state=1,plrdistfurther=300:animate=1,state=1
:state=1,plrdistwithin=40,rateoffire:rotateplr,animate=92,plraddhealth=-20
Use that as the zombie's script and set the door to doorremote.fpi.
EDIT 2:
If you want the door to be destroyed you can modify the doorremote script to destroy the door when activated instead of open it.
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