dzeX11: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/dzeX11 - from package: cernlib-packlib
/usr/lib64/cernlib/2006-g77/bin/dzeX11 - from package: cernlib-packlib

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/dzeX11 - from package: dzedit

You may install the required package with command apt-get install {package}

Error in other languages:
dzeX11: bevel nie gevind nie
dzeX11: comandă negăsită
dzeX11: comando não encontrado
dzeX11: commande introuvable
dzeX11: command not found
dzeX11: käsku ei ole
dzeX11: không tìm thấy lệnh
dzeX11: komanda nerasta
dzeX11: Kommando nicht gefunden.
dzeX11: kommandot finns inte
dzeX11: komut yok
dzeX11: nie znaleziono polecenia
dzeX11: níor aimsíodh an t-ordú
dzeX11: no se encontró la orden
dzeX11: no s'ha trobat l'ordre
dzeX11: opdracht niet gevonden
dzeX11: parancs nem található
dzeX11: perintah tidak ditemukan
dzeX11: príkaz nenájdený
dzeX11: příkaz nenalezen
dzeX11: команда не найдена
dzeX11: командата не е открита
dzeX11: 命令找不到
dzeX11: コマンドが見つかりません