Not many sources mention the Zion Mule Corps (of the British Army; 1915) and even fewer go into details, but from time to time a certain symbol (see below) of a double-ringed Star of David/6 pointed star with a dot in the center is attributed to the force:

- as illustrated in Alex Friedman's 2nd edition of "Jewish Cap Badges"

- as illustrated in his 3rd edition

- as shown in Ever HaDeni's book "A Nation and Its Wars, 1915-1945"
I believe this symbol was not a unit emblem and for this I'm relying on Ever HaDeni: his book relies heavily on first hand accounts and interviews, and he mentions in passing (page 32) - almost as a curiosity - that the unit commander Col. Patterson mentioned in his book "With the Zionists in Gallipoli" how a "Jewish artifact" was found on the peninsula: while members of the battalion were collecting stones in order to build a dry-kept building in preparation for the winter they found a monument stone with a Star of David engraved into it. Impressed with the symbolism of their find they placed it in a central location in their camp as a monument.
That's all HaDeni has to say about the emblem although his caption for the enclosed photograph is "The Symbol of the Battalion" - I think he meant it figuratively. Elsewhere, much earlier, he writes (page 16) that the symbol of the battalion was a Star of David (I think he means a flag with the Star), and later he writes (page 31) that for burial ceremonies of its members the battalion draped a Star of David with the word "Zion" (in the center) - a common symbol of the Zionists in that period - over the grave.
As far as I've seen (or not) the Zion Mule Corps did not wear any special insignia beyond standard British Army emblems.
Alex