When should I use A or An before words starting with a silent z?

When should I use A or An before words starting with a silent z?

You should use "an" before words starting with a silent "z." The use of "a" or "an" depends on the sound that follows the article, not the actual letter. Since the sound of "z" is a vowel sound in words starting with a silent "z," such as "hour" or "honor," you would use "an" before them.