It seems that the component has been written worng. All images of the placemarkers are plced in administrator/components/com_zhgoolemap/assets/icons
For most sites this will be working, but pro sites that are protecting the administartor directory with htaccess password have issues with it. The resoures could not be loaded.
Images that need to be showed on a site must always be either on /components and then their asset folder or in the /media/com_zhgooglemap/icons. Never, never place frontend CSS/images in the administrator folder.
How can I solve this that the icons are placed in the proper folder?