No more than 6600-ish but accounting for normal attrition, non-primary account closures, general clean-up I'd conservatively say 3300 have been displaced this month so far. Approx 1000 zz'd between 0001 and 0900 on 3/22, approx 1500 zz'd 3/21 + 3/22. For the entire month of March approx 6600 zz'd. This is all based on the ZZ being added and last modified date of the account. So toss 50% and you're at 3300-ish for the month of terminations.
Literally anyone with a domain user account can pull this information.