@Adam_Sw3 the two Z motor connectors on Duet 2 are connected in series. You could connect two motors in series to one of them, to put all three in series. Google "wiring stepper motors in series" to see how.
If they are low current motors (e.g. rated at 800mA or less) then it would be better to wire all three motors in parallel to one of the connectors, and put the two jumpers in the other.