Using two feeders at the same time I am using Prusa i3 MK2s with the first version of the multi-material add-on.

As far as I understand, the slicer defined the used feeding motor using the T0-T3 code which defined one feeder at the time.

Is there a way to have two feeder motors working at the same time?
The first multi material add-on version off J. Prusa includes several separate steppers that load filament into the hot end. Note that selecting an other color will retract the existing filament so that the next filament can be loaded. There is no mixing hotend nozzle. It is therefore working serial, not parallel. Working 2 steppers at the same time will  lead to clogging the filament joining position.