I got my first S Rank on zone 7, but I wasn't recording. I wanted to get a recreation of it first before upgrading any of my units to be stronger than they were at this exact moment, because I think my investment levels right now are really funny.
I skip Koleda's chain attack because it just doesn't do enough damage to justify using over more Zhu Yuan field time. In my original clear, I was around 10 seconds slower on my first side due to warp spam, so my second side had to be super optimized to make it, and I found that skipping Koleda's chain attack would give me the extra 5 seconds I needed over the course of the boss fight. Second side has the capability of clearing in 1:10 but I have to be reasonably lucky as well as not flub my inputs as much as I did here
0:00 Starting run
0:10 First side - Mobbing
0:40 First side - Boss
2:55 Second side - Mobbing
3:20 Second side - Boss
6:23 Builds
7:19 Remembering that skill levels are a part of builds