Before you apply anything from anywhere, including this forum, establish what your machine is currently doing. In the majority of cases the answer is visible in this list and no registry editing is required.
- How many startup entries exist, and how many do you actually recognise?
- Is a management or inventory agent installed and trying to reach a server it cannot see?
- Is storage healthy, and is the drive close to full?
- Is the machine thermally throttling within a minute of sign-in?
- Has a driver changed recently, particularly storage or graphics?
- Is a security scan running immediately after sign-in every time?
Post the answers along with your model and Windows build and you will get a far more useful response than "my ZBook is slow".