There are two ways to make multiple valves run at the same time. One is to use the ‘master zone’ feature. You can define up to 2 separate master zones, and have every zone associated with one or both of them. This way, when a zone is activates, its associated master zone(s) will also be activated. You can also adjust the time the master zone(s) will fire (for example, opening a few seconds after a zone is activated or closing a few seconds before a zone is deactivated etc.). The master zone is handled automatically.
If that’s not sufficient for your need, you can go with parallel zones: if you tick off the ‘sequential’ flag of a zone, that becomes a parallel zone and is allowed to run at the same time with other zones. You can set programs that include multiple parallel zones and they will all run at the same time. For example, if you have zone 1 as a parallel zone, and zones 2 and 3 are sequential, then in a program you can set zone 1 to open for 5 minutes, zone 2 to open for 2 minutes and zone 3 for 3 minutes. Then when the program runs, zone 1 will start together with zone 2, and continue running until zone 3 finishes. This is a more manual way to schedule multiple zones to run at the same time.