"Yuppie" is generally used as a noun, not an adjective.
For Z: zippy (to describe a fast car)
Have you been asked to do this for an exercise? If so, it's completely unfair of them to have included the letter "X". There are very few words which start with "X" anyway and I don't think any of them are adjectives. I understand most of the ones that you have used rather ingeniously, but I have no idea what "Xenial" is meant to be.
Student or Learner