What It Scores
ZO is a valid word in the tournament list this site uses. Tile values only, before any premium square: 11 in Scrabble and 11 in Words With Friends. The letters break down as Z10 O1.
Longer Words Containing ZO
ZO appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.