I'm sure Adriana gets it on the regular (otherwise Zo is gay), Mel and Emily not so much probably.
Mel says it's been years, as does Emily. They even haven't slept together since college.
Zo and Adrianna seem close, but that has mostly been around the kids. I seem to recall some Adrianna thoughts about things not being great. Zo is working a lot lately, and they may be drifting apart, or having a slowdown in sex. If Zo ends up being involved in the shady shit going on with Ethan and now Zach, maybe he's getting model action on the side.
Incidentally, maybe Zach is Val's way out of the situation with Ethan? He does like her, and is getting set up with her... Maybe Zach will get a redemption route before he dies?