zegrep: 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/zegrep - from package: gzip

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

On Debian possible default full paths are:

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

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

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