I have a ZKK-602 .416RM and a CZ-550 .458 Lott. There is only 2 differences between the actions... the stock is another thing. But anybody can upgrade a stock to improve a rifle.
The ZKK-602 has a "funky" backwards safety. It's the same idea as the simple Rem M-700 safety, a small thumb actuated lever on the side, but back is fire, forward is safe.
The CZ-550 has reversed the travel direction of the safety to make it function virtually identical to a Rem M-700. The only other actaul difference between the ZKK and the CZ is the shroud on the safety of the CZ has been modified, which is merely cosmetic.
Personally I prefer the appearance of the old ZKK-602 over the so-called modern look of the CZ-550. But there is really no difference. Just get used to the direction of the safety. I guess you could get it modified (on the CZ-602).
The stock on my CZ-550 .458 Lott is butt ugly, but it's functional so that's all that matters. That rifle weighs 9.5 lbs, with just the factory express leaf sights, but I can shoot it pretty decent at 100 yards off-hand. It is a great shooting rifle (as is the .416RM).
I have a Leopold 1.5-6X Vari-XIII on the .416RM and I took a nice bull moose with it at 200 yards last October.
If you are worried about the stock, and I can understand that, then just upgrade it. You will not find a better action then the CZ-550 for the money.