I use Gut Hooks every time. I have one that zips the hide.
I don't recall ever seeing a tool used for zipping the hide other than my knife.....can you post a pic/link?
I have an 'old' Winchester brand skinner with gut hook. It's g h is on the larger size and works great on zipping the hide.
I have a Remington lock folder with a small gut hood. It's great for opening the body cavity.
The Win is a great skinner and the larger gut hook works 'better' on the hide.
The Rem gut hook is smaller and is better on the thinner abdomen layers w/o 'hooking' the entrails.
Both g hs can be sharpened with a ceramic stick.