The Brief: ZOMG is a synonym for "OMG."
The Z in ZOMG does not stand for anything; it simply stylizes OMG. It is used to show emphatic or overwhelming emotions, such as euphoria. It can also be used in response to something cute, as one might use uwu.
ZOMG @NostalgiaBath I found the greatest gif of all time
— Neil Shurley (@ThatNeilGuy) February 25, 2019
ZOMG! I'm so excited!! 🥳🎉🎊☀️ https://t.co/kXxka1jaL3
— Ian Coldwater 👻🌿✨ (@IanColdwater) February 25, 2019