Is it clear to you that almost all Zentyal feature could be covered managing applications and components having, for most of then, module in Webmin?
I mean: if Webmin is mandatory and conflicting with Zentyal, why do you want to run both in parallel?
I know I'm a bit provocative here
but goal it to make you reacting: what do you have with Zentyal that is missing in Webmin?
- If you know LDAP, you can manage accounts (users) and groups using Webmin (and do much more that Zentyal does)
- you can manage Squid, Squidguard, firewall, DNS, DHCP, Postfix, Dovecot, Spamassassin, Samba... well, almost everything with much more parameters and flexibility assuming you understand the very detail of those products and applications.
On the other hand, if you don't know the very detail or don't want to bother with hundreds of parameters and if Zentyal scope fits your needs, why would you take the risk to break something while using Webmin in parallel of Zentyal. Here again I'm a bit provocative but not that much
I'm not saying Zentyal is perfect
but feel that Zentyal and Webmin are not on the same shelf and not targeting same kind of user or same kind of deployment. Trying to have both at the same time is somewhat strange to me (yes, I do understand that Webmin brings some added value, I'm using it too.... but not on my Zentyal server.... anymore