lzdiff: 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/lzdiff - from package: xz-lzma-compat

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

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