nmzmerge: 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 Debian possible default full paths are:

/usr/bin/nmzmerge - from package: namazu2-index-tools

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

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