Hey @Mikespring!
Two zones can be wired in the same slot- this is assuming you do not have a master valve. You controller cannot support three valves running simultaneously. Also, as @GregS stated, you must have the sufficient water pressure to support two zones. This is an issue some users ran into when trying to run two zones at the same time. This thread has quite a few users that run two zones simultaneously successfully and some other tips if you want more info! Let me know if I can answer any other questions.
McKyzee 
