Upon first thought, you might think that there are no words ending in z. However, that is not correct. True, the majority of words do not end with the letter z. Lots of them, such as faze and maze, have z as the second to last letter. Yet it is unusual for a word to end with the "zzzzz" sound, which is why people tend to think that there are very few words that end with z.

Here's a list of some words that end in z. Perhaps you can come up with even more suggestions on your own!
So do many of those words look familiar to you? Chances are, they don't. A lot of them are technical terms or words that have to do with a specific discipline. Don't fret though! There is no rule that says that you must use words that end with "z" in your writing. It is better to use a word that is appropriate, than to force in a word that ends with "z" just to be able to say that you have done so. In fact, that rule applies for all components of writing. Do not force a technique upon your writing. Let the technique naturally flow from the words that you have chosen.
Another important note to keep in minding when working with these words is to avoiding overdoing it. That means you should not throw tons of words that end with "z" into your writing. Unless of course, you are doing it in order to obtain a specific effect (alliteration, for example). If you merely throw a bunch of words ending with "z" onto a piece of paper, it is not going to look as though you have written a well polished piece. Instead, your working is going to look like a zany zoo of z's!