calendly, which then writes it to google calendar.
So the question is how zapier will know if they schedule. Does zapier do calendly? If so, you can edit the first zap so it also adds a row in a google sheet when they fill out the screener (with their name, email, and whatever info you want). Then you could run a zap when someone schedules with calendly which finds their row in the google sheet (based on email address?) and marks in a column that they scheduled.
Then you could edit the first step so that it ways a few days or a week, looks up their row in the google sheet, checks if they scheduled yet, and if not, sends the email.
Let me know if you need any further help!