On my Ultima I'm using a Tilton pump designed for the purpose, they are not overly expensive.
Virtually all the transaxle cooling/oiling systems I know of spray the oil back to the gears. I am not familiar enough with the intricacies of the ZF, but I'd want to be sure the ZF ring & pinion housing has enough free flow back to the gearbox that you cannot pump the gears dry. Oil flow may be compounded by the fact the ZF was not originally designed to run in our (Pantera) orientation.
Julian
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