To mount a scope on your CZ 457 or older CZ rimfires (CZ 455, CZ 452 & others) - you need a scope mount.
There are two types of scope mounting solutions:
- scope mounts that attach directly to the 11mm dovetail ~ you just get the scope mount and mount it directly to the rifle dovetail, and
- scope mounts that attach to picatinny rail ~ if your gun is equipped with picatinny rail from factory, or if you got picatinny rail attached to your rifle as an aftermarket upgrade (such as these), you can use scope mounts that install to the picatinny standard.
As with everything, there is no universal best option and the decision which mount to use shall be based on your preferences and intended use of the rifle. Below we go into detail of both of these options. 
Dovetail scope mounts
Dovetail scope mounts only come into consideration if your CZ rifle is not equipped with picatinny rail from factory (such as CZ 457 MDT). If your CZ rifle is equipped with picatinny rail from factory, you can skip this section and go directly to scope mounts that attach to picatinny rail. If your rifle is not equipped with such rail, you can still get one as aftermarket upgrade and then install scope mount with picatinny standard mounting.
Dovetail scope mounts attach directly to the dovetail with claps. These mounts are different for each CZ rifle as they have different sized dovetail ~ therefore you can find different dovetail scope mounts for CZ 457 models, and different for other CZ rifles.
Its also worth mentioning that dovetail scope mounts may be the only solution how to mount a scope to older CZ rimfires, incl. CZ Brno, CZ 452 & other. The reason is because although these older CZ rimfires have the same dovetail as new CZ rimfires, the position of eject window is different for each model. Since dovetail scope mounts are usually made as two separate mounting rings and can be mounted directly to the dovetail, you will be able to to install these mounts regardless of the position of eject window and thus be able to mount a scope even on older CZ rimfires. I.e. new made dovetail scope mounts can be mounted to old CZ rimfires, but new CZ picatinny rails (as CZ 457 picatinny rail) cannot be mounted to old CZ rimfires due to different position of eject window.
The main negative with dovetail scope mounts is that there are not so many options available. For example if you are looking for special scope mounts that allow quick detach by lever, or tactical mounts that have addition rails for mounting a red dot, you will not be able to find such mounts with dovetail mounting. Instead you will have to go for scope mounts with picatinny rail mounting as there are more options due to standardisation. If you do not need any of those features though, the dovetail scope mount will work perfectly for you. 
Picatinny scope mounts
Picatinny scope mounts use picatinny standard for mounting. To use such scope mount, you will need to have a picatinny rail on your CZ rifle. That can be either from factory (such as CZ 457 MDT), or as an aftermarket upgrade installed to your dovetail(such as picatinny rails here). Once your CZ rifle is equipped with such picatinny rail, you can mount any picatinny scope mount to the rifle. Given the standardisation of the picatinny mounting system, there are many more picatinny scope mounts available.
Picatinny scope mounts are being made in various heights, with various mounting mechanisms allowing quick detachment, with additional rails allowing mounting of extra red dot to the scope mount, with various angles, etc. These picatinny scope mounts are being made as one piece device (such as this) as well as two separate scope rings (such as these).
