[Setup] Says I need Zlib, but I already have it.

[Bob Ross]

Any ideas of what else I can do?

The install log only showed date and time ran. No detailed error.

#: sudo ./install.sh zeo
ZEO Cluster Install selected

Detailed installation log being written to
/home/ec2-user/WebSite/Plone-4.2.5-UnifiedInstaller/Plone-4.2.5-UnifiedInstaller/install.log

Note: libz library and headers are required for the install.
The package name for this may be zlib-dev.
Exiting now.

#: sudo yum install -y zlib-dev
Loaded plugins: priorities, security, update-motd, upgrade-helper
Setting up Install Process
No package zlib-dev available.
Error: Nothing to do

#: sudo yum install -y zlib
Loaded plugins: priorities, security, update-motd, upgrade-helper
Setting up Install Process
Package zlib-1.2.5-7.11.amzn1.i686 already installed and latest version
Nothing to do