I get that Zucker was a disappointment, but he finished the year with a pace of 20 goals and 40 points per 82 games. I'd prefer he be better than that, but that's also almost exactly what he did in 2018-2019 with the Wild (21 goals and 42 points in 81 games). He hasn't been worth what they paid for him, but he's still been a good player for them overall. They paid top-6 winger prices for a guy who ended up a 2nd/3rd line tweener here, it's not great but it's not the end of the world.
He'll probably be taken in the expansion draft, which helps the Penguins cap situation and lets them lose a guy they can afford to lose. All things considered, I'd make the trade again even with him being a sub-optimal fit with Malkin. The thought of keeping Addison (who the Penguins didn't need) and the 1st rounder (who won't help the Penguins with Crosby and Malkin) isn't worth giving up Zucker, even if he's not a great fit here.