Trebor practiced form VI, the diplomat's form. It eased off the lightsaber focus so a Jedi could concentrate more on other skills. Zett's form I could not find anywhere reliable on the Internet, so from what we see in RotS, I would say he's form IV or V.
Trebor is more aware of the Force's will, as a master, but I wouldn't assume him to be stronger, necessarily. Zett could have more raw potential, even when untrained, means faster reaction times.
There are many things we can't be sure of in this match-up.
My gut tells me Zett.