The correct command to remove php 5.2 before upgrade zend server to 5.3 is
yum -y remove zend-server-php-5.2 && yum -y remove `rpm -qa|grep zend|xargs`
Use yum -y remove zend-server-php-5.2 is not enough.
After removal, run
yum install zend-server-ce-php-5.3
Of course, zend repository must be add to /etc/yum.repos.d before. (If not, where you got zend server php 5.2?)
The most recent /etc/yum.repos.d/zend.repo is
[Zend]
name=Zend Server
baseurl=http://repos.zend.com/zend-server/rpm/$basearch
enabled=1
gpgcheck=0[Zend_noarch]
name=Zend Server – noarch
baseurl=http://repos.zend.com/zend-server/rpm/noarch
enabled=1
gpgcheck=0
I notice it was changed since my first copy. It was
[Zend]
name=Zend CE $releasever – $basearch – Released Updates
baseurl=http://repos.zend.com/rpm/ce/$basearch/
enabled=1
gpgcheck=0
[Zendce-noarch]
name=Zend CE – noarch
baseurl=http://repos.zend.com/rpm/ce/noarch
enabled=1
gpgcheck=0
Old copy no long work with command
yum install zend-server-ce-php-5.3