zfgrep: 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/zfgrep - from package: gzip

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

On Debian possible default full paths are:

/bin/zfgrep - from package: gzip
/bin/zfgrep - from package: zutils

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

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