I’ve been using Zammad for some time now, so I haven’t invested time into workflows which was added after I started using it. I believe you can do this using them as @skip suggested.
I use Email Filters for stuff like this as it applies to the email before creating the ticket.
Triggers are great for managing changes to current tickets.
Email Filters are great for addressing emails that come in before creating the ticket.
I use an email filter to check for a specific subject and if it exists, assign it to a specific group and category.
I believe that you can make agents, agents for specific tickets and customers for others. I think this would be done in the user profile. I haven’t done this myself though.