The reason that words like UQUQ, ZEN, and CUZ are not in the Official SCRABBLE Players Dictionary (OSPD) nor in the Official Tournament and Club Word List (OWL) is that they have not appeared as lower case, non-apostrophized, non-hyphenated, non-foreign, single-word entries in any of the source dictionaries that were used to create and to update these official SCRABBLE lists. The four college level source dictionaries used to create the OSPD4 and the OWL2 were:
Also, for the original OSPD one other source dictionary (Funk & Wagnall's Standard College Dictionary, 1974) was one of five sources used, and some words from earlier editions of the OSPD have been grandfathered as explained in the Dictionary Committee page. Since these sources are all abridged dictionaries many valid words that are not as frequently used do not appear in them.
The best way to get words into a future edition of the Official SCRABBLE Players Dictionary (and the Official Tournament and Club Word List) is to convince the editors at Merriam-Webster to add them to Merriam-Webster's Collegiate Dictionary which has always been one of the source dictionaries for the OSPD official words.
Jim Lowe, Senior Editor at Merriam-Webster, Inc. suggests sending a dozen or so documented print usages of the proposed words to them for their citation files. Google Books is a great way to find citations. At that point the editors will do additional research to determine the advisability of inclusion of the new terms into Merriam-Webster's Collegiate Dictionary.
The mailing address is:
Merriam-Webster, Inc. 47 Federal Street P.O. Box 281 Springfield, MA 01102
When the next edition of the Official SCRABBLE Players Dictionary is done the new words that have made their way into Merriam-Webster's Collegiate Dictionary should then be incorporated into the OSPD and thus become legal words for tournament and club play.
In international play, a similar process is followed by HarperCollins Publishing to prepare the larger Official Scrabble Words lexicon. Comments concerning that list should be directed to the International Committee for forwarding to the WESPA Dictionary Committee.
As for your group using these words as you play, that's the great thing about SCRABBLE Brand Crossword Game — if you and your opponents agree on the dictionary or word list you want to use then you are by all means free to do so. Of course, if you play at a NASPA club or sanctioned tournament then the word list used for adjudication there would be the OWL2. (If you cannot get all of the people in your group to allow these words in all the games you play, you might want to suggest including them as acceptable in a certain percentage of designated games. It could be a fun variation for your group from time to time.)
We hope that you and your friends continue to enjoy playing SCRABBLE Brand Crossword Game whatever word source you choose to use.