"省略中间的音节" can be translated into English as "omit the middle syllable(s)" or "elide the middle syllable(s)".
"Omit" means to leave out or exclude something.
"Elide" is a more technical term in linguistics, referring specifically to the omission of a sound or syllable in speech or pronunciation.
Both expressions are correct, but "omit the middle syllable(s)" is more commonly used in general contexts, while "elide the middle syllable(s)" might be preferred in more technical or linguistic discussions.