Learn French: Ils sont chez eux maintenant.

Eux is a stressed pronoun, which means "them" for a masculine or mixed group. In French, you must use a stressed pronoun after prepositions like chez (at the place of), avec (with), or pour (for). You can never use subject pronouns like ils right after a preposition, so you must say chez eux, never "chez ils".

How does chez eux translate to "at home"?

The word chez means "at the home of" or "at the place of". When you combine it with eux (them), it literally means "at the home of them" (at their home). Because the subject of the sentence is already Ils (They), "at their home" naturally translates to just "at home" in English.

If the group was all women, would it be "Elles sont chez eux"?

No, you would say Elles sont chez elles maintenant. Eux is the stressed pronoun specifically for masculine or mixed groups. If the group is entirely female, you must use the feminine stressed pronoun, which is elles.

Do I pronounce the 'z' in chez when saying chez eux?

Yes! Because chez ends in a silent consonant and eux starts with a vowel sound, you must connect them when speaking. This is called a liaison. It sounds like "shay-zuh".