Ad. [ōu] and [ēi] became over-long [ō] and [ē]; [ōu|ēi] > [ō|ē]

Ad. [ōu] and [ēi] became over-long [ō] and [ē]; [ōu|ēi] > [ō|ē]
Of the original long diphthongs, two of them, [ōu] and [ēi], were reduced to over-long simple vowels [ē] and [ī], respectively (SD/424). Presumably, like other over-long-vowels, they were reduced to ordinary long vowels in Classical Adûnaic.

Reference ✧ SD/424

Phonetic Rule Elements

[ōu] > [ō] ✧ SD/424 (ÔU > Ô)
[ēi] > [ē] ✧ SD/424 (ÊI > Ê)

Phonetic Rule Examples

izrēi > izrē ēi > ē ✶Ad. izray+yi > izrai+yi > izrēyi > izrêi > Ad. izrê ✧ SD/424