zf: 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/zf - from package: php-ZendFramework

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

On Debian possible default full paths are:

/usr/bin/zf - from package: zendframework-bin

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

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