Here you will find words, phrases, sentences, and paragraphs for practicing the "z" sound. Most of these are taken from the Home Speech Home site. This sound is very similar to the "s" sound except that we have to "turn on" our voices.
https://www.youtube.com/watch?v=1tfDIQCYOkc
"Z" Picture Words Initial "Z"
"Z" Word Lists Initial "Z"
"Z" Phrases Initial "Z"
"Z" Sentences Initial "Z"
"Z" Tongue Twisters This is a zither. Is this a zither? Zizzi's zippy zipper zips Zithers slither slowly south