you should perhaps open a new dedicated thread
Anyway, I gave a try and indeed it doesn't work for me but it looks like poor LDAP plugin implementation.
I got an error while configuring using web interface after my first try returns 'wrong ldap filter"
Since I can't modify anything.
I tried configuring schootool.conf.
From ldap standpoint, your ldap section should look like this:
# autodetect_from /etc/ldap.conf
# default_login_attr uid
# default_login_filter objectclass=posixaccount
query_users uid ou=Users,dc=zentyal-domain,dc=lan?one?(objectClass=posixaccount)
#bind_group teachers 7001
#bind_group 2011-2012 students 6024
but I can't test further and don't know how to reset conf.
BTW, for some reason, I never had good experience with Zope and LDAP... there is no obvious reason but so far..
EDIT: fixed copy/paste error with "groups"