How to pronounce The /z/ as in ZOO /z/ in American English

The only difference is vocal cord vibration. If you place your fingers on your throat and say a long ssss, you won't feel anything. But if you switch to a long zzzz, your throat will buzz like a bee. Your tongue, jaw, and lips stay in the exact same position for both. If you ever struggle to make a /z/, start with an /s/ and simply turn your voice on.

In American English, when you add an 's' ending for grammar, making a noun plural (dogs, shoes) or conjugating a verb (plays, runs), the S is pronounced as a /z/ if the sound right before it is voiced (unless that sound is itself a hissing sibilant like J or Z, which adds an extra syllable instead). Because vowels are voiced, words ending in a vowel sound take a /z/ suffix. Just remember this rule only applies to grammatical endings. For base words that happen to end in the letter S, the pronunciation varies: words like is, was, and his use a /z/, while bus, this, and yes keep a sharp /s/.

You are likely cutting off the vibration too early, which turns a word like eyes into ice or buzz into bus. In American English, a /z/ at the end of a word also makes the vowel right before it noticeably longer. To fix this, stretch out the vowel a little more than you think you need to, and keep the final /z/ gentle. You don't need to force a heavy buzz all the way through the end of the sound. As long as the vowel before it is noticeably long, the word will be heard as a /z/, not an /s/.