Three years ago.

[TecmoBengals]

Bringing up how Marvin didn't have the benefit of free agency since Zac is the first Bengals coach to benefit from the Brown family embracing free agency isn't really a necessary talking point when comparing the two coaches. This take is rooted in my opinion that Marvin was a far better coach than Zac Taylor currently is and likely turns out to be based on W/L %.

Marvin Lewis:
Games - 256
Wins - 131
Losses - 122
Ties - 3
W/L % - .518

Zac Taylor:
Games - 41
Wins - 11
Losses - 29
Ties - 1
W/L % - .280

This info is from: https://www.pro-football-reference.com/teams/cin/coaches.htm

Zac has a ways to go to join the Bengals coaches who hovered around the .500 mark: Marvin Lewis, Sam Wyche, Forrest Gregg, Bill Johnson, and Paul Brown. Zac is among the ranks of Dick LeBeau, Bruce Coslet, David Shula, and Homer Rice as coaches with really bad W/L records (1992 to 2002 was a horrible time to be a Bengals fan).

Note, I do think it was time to move on from Marvin Lewis, so my claim that he is better than Zac is not an endorsement for Marvin's continued tenure. Time will tell if the Bengals landed a gem with Zac, but it isn't looking good. As fredtoast implies, or maybe stated if I overlooked his post, Marvin might have had even a better chance at winning if the Brown family embraced spending big dollars in free agency during his coaching tenure.

Edit: Botched the end of my post saying Marvin won 250+ games, he didn't.