Zuul appears as a 10' tall, spindly-limbed, sexless humanoid.
The face is almond-shaped, with large, pupil-less eyes that seem to take in everything, everywhere.
The ears are long, thin, & Elven, except that they seem to extend back from the head like a dragon's.
The nose is a thin, hawk-like ridge with the barest hint of nostrils.
The lips & chin bones are almost razor-thin & gaunt - as if the barest effort were spent to form them.
The skin is best described as "Mother of Pearl" - it's white, but with the faintest hint of colours within colours.
The hair is soft, flowing, & wheat-coloured, braided into a long, thick tail that reaches nearly to the floor.

The torso seems slightly oddly ridged at first, until Zuul stands up & you realize what the "ridges" are.
Zuul has six arms that have no true joints & can bend in any direction where a humanoids flex points would normally be.
(The "ridges" were where the other four arms were folded behind.)

The legs are also jointless, and seem... odd... somehow.
(The also bend in ways that tend to make humanoids slightly queasy to watch.)
The fingers are longer than a human's, & seem infinitely more dexterous - as if they could pluck dust motes from the air with ease.
Due to the limberness of Zuul's appendages, there is no "off hand", no "place where it itches that I can't reach", 
& no penalty for climbing walls, ceilings, or weilding the strangest of things.
Like a weapon in three hands, & spells in three others, for example...

Zuul does not truely speak.
Zuul is telepathic (range infinite, even across Planes) & can "speak" with anything that has a language of its own.
Therefore, Zuul's "voice" is heard as a soft whisper, like liquid bubbling up through a deep-water spring, coming from deep inside ones own mind.
Anyone within 100' of Zuul must Will Save (DC 549) or be under the affect of a "Calm Emotions" spell.
Anyone who makes a successful save must then also make a second Will Save (DC 549) or go completely insane.
(Either it Calms you & you're fine, or it drives you completely insane "hearing voices in your head".)

Zuul normally does not enter combat, preferring to use Diplomacy & Intimidation to make a potential combatant go away.
Failing that, one Maximized, Heightened, & Epicly Enhanced "Elemental Blast" to the chest tends to remove them quickly.
(100' Ranged Touch Attack, deals 100 Dam *of each Energy type* [A/C/E/F/S], entirely Divine & unavoidable.)
Should this still fail to convince the atagonist to leave, Zuul resorts to physical violence.
Lots of it.

Zuul uses two hands as a Monk, Epic Whirlwind & Great Cleaving through all that stand in defiance.
The other four hands cast devastating magical energy where it will do the most damage in the shortest amount of time.

In short, when Zuul is happy, everything's cool.
When Zuul is angry, Roll A New Plane.