FS-1-WL: Can you use this wireless pedal with the EV-1-WL at the same time?

Unfortunately, this is not possible.

If you choose to use the FS-1-WL wireless, you can add an extra control pedal by connecting this pedal to the CTL connection of the FS-1-WL.

The compatible pedals for CTL connection are:

For more info on the FS-1-WL and EV-1-WL: