Zadorov doesn't have a track record of being a top 4D on teams with a strong defense, the numbers don't bear that out.
His ice time throughout his tenure in Calgary, who had a superior D at the time, indicated he was a 5.
21-22, Zadorov ranked 6th in ATOI for Calgary D regulars behind Andersson, Hanifin, Tanev, Kylington, and Gudbranson. Averaged 16:55. Stone actually averaged more time on ice than Zadorov did too with 17:27, but he only played 11 games.
https://www.hockey-reference.com/teams/CGY/2022.html
22-23, he ranked 5th behind Andersson, Hanifin, Tanev, and Weegar. Averaged 18:41.
https://www.hockey-reference.com/teams/CGY/2023.html
Even this past season he ranked 5th in ATOI for Calgary D regulars behind Andersson, Hanifin, Tanev, and Weegar. Averaged 18:24.
https://www.hockey-reference.com/teams/CGY/
Zadorov topped out as having the 3rd highest ATOI amongst D regulars on a lousy Blackhawks team behind Keith and Murphy. Averaged 19:12.
https://www.hockey-reference.com/teams/CHI/2021.html
Go back to 19-20 with the Avs and he ranked 5th in ATOI amongst D regulars behind Girard, Johnson, Makar, and Graves. And even then, he only beat out the 6th ranked guy in coal by 4 seconds. Zadorov averaged 17:46 while Cole averaged 17:42.
https://www.hockey-reference.com/teams/COL/2020.html