According to my testing, almost all original files which have been zipped were removed, except one or two, based on the above simple changes. My test periods included per minute/hour/day. That is, an 99% job would be done. We don't really care about a little deviation from the perfection. We have an automation app which creates a large number of log files with huge sizes(10MB each). An auto zip compression (about 95%) is absolutely necessary and it saves a lot storage space for us.