What are some alternatives?
When comparing ZPanel and cPanel, you can also consider the following products
Webmin - Webmin, Usermin, Virtualmin, Cloudmin, Linux, System Administration
Plesk - Plesk puts all the automation, security, and technical tools an IT professional needs in one simple and easy to use dashboard.
DigitalOcean - Simplifying cloud hosting. Deploy an SSD cloud server in 55 seconds.
Sentora - Sentora is an open-source web hosting control panel built specifically to work on a variety of Linux distributions. Sentora is licensed under the GPL and is a separately maintained fork of the original ZPanel project.
Hostwinds - Hostwinds offers web hosting services and solutions.
Virtualmin - It includes numerous features not in the GPL version (like script installers, resellers, HTML editor, an improved UI, mobile access, spam and virus filtering).