AppZapper, AppCleaner, TrashMe, and similar apps do not do a thorough job of removing all files/folders related to deleted apps. I tested several of these, using Skype as the app to be removed. Of 17 items to be removed:
AppZapper missed 13 items
AppCleaner missed 11 items
AppDelete missed 8 items
Hazel missed 9 items
I also tested AppTrap, CleanMyMac and a few others, but don't recall how many items they missed. All left files/folders behind. In most cases, they remove .plist files and a few others, but leave behind much larger files and folders. (you will find a discussion of these tests in the thread linked below)
One app that I would
not recommend, based on the number of complaints that have been posted in this forum and elsewhere, is CleanMyMac. As an example:
CleanMyMac cleaned too much
The only effective method for complete app removal is manual deletion: