Cuneiform for ze, zi, and ZI; digitized form.Old Assyrian cuneiform for ze, zi, and ZI.EA 26, fragment (Obverse). (high-resolution expandable photo) (Last flat-surface 5-lines on fragment (Para IV), lines 30–34. (An Amarna letter that uses zi.)
The "zi" sign has the syllabic usage for ze and zi, and a Sumerogram usage for ZI. Alphabetically "zi" can be used for z ("z" can be interchanged with any "s"); and "zi"/"ze" can be used for i, or e. In Akkadian, all 4 vowels, a, e, i, u are interchangeable with each other.
Epic of Gilgamesh usage
The zi sign usage in the Epic of Gilgamesh is as follows: ze-(6 times); gi-(46), ZI-(32 times).
References
↑Parpola, 1971. The Standard Babylonian Epic of Gilgamesh, Sign List, pp. 155-165, no. 084, p. 156, "zi".