zoom-in shortcut

I switched my layout to Swiss French and immediately the shortcut for Zoom in changed to Commmand-!, both in Preview and in Safari. It also changes when using Swiss German.

The shortcut remains as Command+

for several other layouts that I tested: US, Portuguese, French, Belgian, German.

The shortcut hasn't changed except on your iMac. You could try booting into Safe Mode then restart normally.

How to use safe mode on your Mac - Apple Support

Suggest downloading the Application Etrecheck directly from a well Respected ASC Contributor. And Safe to use.

The application is free or paid from added features. 

Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ).

It will take a Snap Shot -  both the hardware and software.

 The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

Ah the " Extra Eyes " to the assistance and would really suggest following the advise of @ Luis Sequeira1 on the Keyboard Layout and experiment

That is Outstanding work and bears recognition IMHO :-)

Mac (Retina 5K, 27-inch, 2017)

Q - Runtime: 5:42.  Performance: Below Average

disk0 - APPLE SSD SM0256L 251.00 GB (Solid State - TRIM: Yes) 

A - Generally not a good sign regarding the Health of the SSD . See more details specific to drive health https://binaryfruit.com/drivedx

Q - System modifications - There are a large number of system modifications running in the background.

A - Any time there are large amounts of System Modifications - this tends to have a Negative Affect on the Normal Operations of the computer. Though, do not see a specific relationship between Performance and the specific " Alternation of the Shortcut" in question.

Hopefully the Extra Eyes on your question may shed some additional light 

Q - Runaway user process - A user process is using a large percentage of your CPU.

Q - macOS Monterey 12.3 (21E230) 

A - Current version is 12.3.1

Q - com.bombich.ccchelper.plist (Bombich Software, Inc. - installed 2021-09-22)

A - Good Rescue Plan and use it myself.

Q - [Loaded] org.xquartz.privileged_startx.plist (Apple Inc. - XQuartz - installed 2021-04-26)

A - https://www.xquartz.org/releases/XQuartz-2.7.7.html Does not appear this Application is not supported on Monterey.

EDITED

What is your keyboard layout?

In the View menu, what is the shortcut that is shown? Did it change there to Command-! as well?

I agree with all the points you make, but I suspect the keyboard shortcut issue is due to the layout in use. I will do some testing by changing the layout on my mac and seeing what happens.

Sorry :-(( - this did not turn out as I had hoped.

No worries! 🤓