I would suggest that your contractor knows better than us how to best take care of your needs. In many cases there are no divisions made. The idea of irrigation is simply to supplement any lack of rain fall. We try to seperate sections based on matching precipitation rates so we can time zones to make up any rainfall shortcomings. If a zone has annuals that require more water than shrubs, simply time the running of that zone to accomodate the annuals. I dought the little extra water on the shrubs would hurt them. Again, please discuss this with the contractor. He is on your site and will know better than us.