As stated in a previous thread, I parse it as a single syllable. Not very exotic, I know.
But for science, let's try another approach.
- Multiple Zs in a row are internationally recognizable as onomatopoeia for snoring.
- When transliterating words, an apostrophe is often used to separate letters or syllables for clarity.
- The Zz'Rot Portals spew Voidspawn - immature Voidborn creatures. Most Voidborn have a distorted vocal tendency as compared to humanoid champions. Cho'Gath sounds like he's speaking with a mouthful of someone, Kog'Maw apparently learned English from Donald Duck, and Rek'Sai just screeches at you. With that in mind, let's apply a throaty guttural R (some call this a French R, although it is common in other languages such as Dutch (LoL fans may recognize Siv HD's pronunciation)).
- It seems unlikely that Voidborn terms would include unnecessary silent characters, so the final consonant is probably a hard stop (rather than a silent t as in escargot).
Now, wouldn't you just love to put that all together and have the casters say that? A snore, a throaty R, a sudden stop. They'd almost be guaranteed to cough up a phlegm ball every time they said the word.
"Zz'Rot... *swallow* ...Portal"