(Originally I noticed the zoom history was storing a list of sites I visited where the zoom level was changed and that's what I started noting in my report here; however, then I noticed per a bug ticket that the zoom history would get purged by using Chrome's "Clear browsing history" function and electing to include "Content settings". Yet CCleaner has no option to include purging of Chrome's content settings - so users are stuck having to use both Chrome's "Clear browsing history" with content data selected and then using CCleaner. A cleaner CCleaner usage would be to have CCleaner do the Content Data purge.)
CCleaner does not erase the zoom level history in Google Chrome. While the stored zoom level is not a privacy issue, having a list of sites that you have visited (where you happened to change away from the default zoom level) is a privacy issue. CCleaner will erase other privacy data, so why doesn't it have an option to also erase the zoom level history?
In Google Chrome, go to Settings -> Advanced -> Content settings, scroll down to Zoom level (or go to chrome://settings/content/zoomLevels), and there you will see a history stored of the sites where you changed away from the default zoom level. Besides a privacy issue, Chrome only lets you delete one site at a time to remove it from this zoom history. That can take a long time if the user has change the zoom levels on lots of web sites.
See http://www.rawinfopages.com/tips/2014/11/reset-chrome-zoom-levels-for-websites/ on how the user must currently and manually delete the zoom history one site at a time.
Firefox cleanup can include the Preferences it stores per site. I remember it is an on-exit cleanup option in Firefox. I don't have Firefox currently installed to see if CCleaner also has an option to purge Firefox's [per-site] preferences settings. It should. If it does, it should have similar options to purge preferences settings in Chrome, like the zoom history.
According to comment 38 in the https://bugs.chromium.org/p/chromium/issues/detail?id=137412#c29 bug ticket where users have been asking for a zoom history cleanup option since 2010, dullweber claims there is now an option to purge Site Settings when purging browsing data from Chrome. That comment was back on Oct 5, 2017 yet there is still no such setting but there is the Content Settings included for purging that data from Chrome; however, that requires that I manually run the browser cleanup from within Chrome. There is no purge-on-exit function in Chrome, and why users have turned to extensions, like Click&Clean (but that is nagware is interferring with presenting a spam page about changes in a new version of the extension instead of going directly to the URL, and bitches Chrome isn't at the latest version).
In CCleaner, why is there no setting for Content Settings to let the user elect to include those settings and histories from Chrome when running CCleaner? Why do users have to resort to navigating through Chrome's menus to purge browsing history instead of using CCleaner?
There is a "Keep local data only until you quit your browser" option under chrome://settings/content/cookies. While it includes cookies and perhaps site data, the zoom history is unaffected by that setting. Plus, if enabled, Chrome will cease to automatically log into the user's Google account when loaded (you will see "Paused" at the top right of the toolbar in Chrome which requires you reenter your password to unpause the sync in Chrome). CCleaner has an option to delete Chrome's cookies and another option to delete Chrome's session data, so why not an option to also delete the content data as well (which will include the zoom history)?
CCleaner is a privacy and cleanup tool. Not including Content Data in cleaning up Google Chrome is a big miss by CCleaner.