When opening Mac standalone executables, I get an error message indicating that the file is damaged. Windows executables created at the same time work fine. What can I do?

This is a known issue with Mac and its Gatekeeper system. If you download a non-trusted application, Mac will change the permissions to execute that app, saying it is damaged. There are three ways to circumvent this issue:
Instead of double-clicking on the standalone file to run, right-click on it and choose "open". This will bypass security, allowing the user to run unsigned applications. The right-click procedure is only necessary the first time that the file is opened. Afterwards, double-clicking will run the tour without problems every time.
Your second option is to send the file through a USB, as the problem only occurs when the user downloads the file in Safari (or any browser, because Safari is the engine for all browsers in the Mac system).
Read here how you can bypass this Mac restriction: https://www.larrytalkstech.com/fix-os-x-damaged-applications-warnings-from-gatekeeper/
The best solution would be to sign the .app file in your system with a valid certificate and then compress that file again. Your users then won't have any problems when downloading the tour executable.