I'm new to sysadmin and this site, but I'll try my best to answer this based on my experience with that distro.
You don't specify what you're using it for, and how many boxes you have to work with (physical or virtual) so we'll say 2 possibilities. First, you just want to run some servers at home and this isn't live and essential to some venture. Then just use one box, with Zentyal, and redundancy and survival is not an issue. Second, this is for some business or operational function and therefore necessary. Then do not host all servers on one box for standard practice reasons.
As to whether to use Zentyal or not overall, it's a decent distro but I wouldn't use the free version for a massive network. The commercial version is much more robust with better support. Having all services on one box is not typically allowed in production networks but from home, it's not as big of a deal and you make the call.
It sounds like you're asking whether other servers can be used on a Zentyal installation. It's still just Ubuntu Linux so you can put anything else on there. But if you want access by way of the web interface, then I believe you'll have to code that into the files (it's written in PHP I think) to allow those additional servers to be shown. Otherwise just access them by CLI and save time.