It is possible to have 2 valves open at the same time, but I think what you are trying to do could be done using the Master Station capability.
I don’t use a master in my operation so it would be good for someone to validate the following:
If you designate Zone 10 (Expander Zone 3) as a Master Station with the Master On Adjustment of -5 (open Master 5 seconds before the zones that use it)
AND specify that Zones 0-9 should Use Master, I think you will get the behavior you are looking for.
When your program runs, the Master will open 5 seconds before the first zone runs. Since the zones all run sequentially the Master will stay open until the last zone finishes. It will then close. You could use the Master Off Adjustment to have it close 5s after the last zone completes if appropriate.