It's actually not that tough... According to an ESPN article, from 1970 through 2019, teams that swept an opponent during the regular season and then faced them again in the playoffs won the playoff game 67% of the time.
Since 1990, there have been sixteen times when a team was swept in the regular season and then met that opponent a third time in the playoffs. The team that swept the regular season went 11-5 (8-7-1 ATS) in the postseason