As per my call to you a few moments ago, my initial diagnosis from your post was indeed correct.
This is a Picatinny/Weaver rail adaptor for the CZ, offering bolt clearance and converting aforementioned 9-11mm dovetail to accept the Digisight weaver mount.
Pulsar do make a OEM 9-11mm mount, which replaces the mount body that comes with your Digisight, and works fine on most air rifle, rimfire etc, however CZ are reknowned for their bolt reach, and you need this extra clearance, which is low enough not to cause any practical height/cheek to stock issues.
I will send this off to you today and will 100% solve your issue.
In my thumb and forefinger is a Digisight weaver block (call it an arrestor block if you will) which fits into the slots of the rail.
If you unscrew the little locating screw on your Digisight weaver mount, you can pop this out and turn it one way for Picatinny, and one way for Weaver (one thicker than the other as the rails are different profile)
My advise on the .17HMR is to remove it, and this gives you a much better adjustment of reach etc, as it is not needed for rimfire calibres.
You said your other rifle has weaver rail already, so keep it in case you decide a swap to the foxing calibre.
Anything you need , just ask and happy to help.
Paul