I think you’re “giving up” on Kakko if you move him for a 3rd round pick or a rental.
I don’t think you’re “giving up” on Kakko if he’s a major component in a Zegras trade. That’s a hockey trade, not selling low.
You also mention Zegras as a C. The versatility is nice, but I’ve seen a lot of people who think his future lies on the wing. I don’t really have an opinion on that since I haven’t seen enough of him. However, being as C is the more valuable position, I think a majority of people projecting him as a W shows that maybe you don’t have a great handle on what he brings long term.
I would think the + on Kakko to get Zegras would have to be significant. I’d certainly be interested in hearing what that is. An “advanced stat” winger who hasn’t shown offensive growth, vs a guy whose proven he can score at the NHL level.