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

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

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