"When do you finish this?"
Translation:מתי אתם מסיימים את זה?
Well, in normal Hebrew you use אֶת זֶה for an unspecified this. In more flowery language you can use זֹאת without the nota accusativi אֶת, based on biblical examples like מי בקש זאת מידכם Is 1.12 who has required this from your hand. Your sentence would make sense after a concrete feminine noun: יֵשׁ לָךְ עוֹד עֲבוֹדָה Do you still have work (to do)? When do you finish it?