Smooth transitions into shift lock

Thanks for your help, but I’m looking for how to do this in a 3rd person perspective
Here’s an example, the gun in this clip. When you hold right click, it will zoom into a shift lock like mode:
https://cdn.discordapp.com/attachments/680019315193675777/743707456257130516/2020-08-14_06-45-48.mp4