cdfzonalsum: 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/cdfzonalsum - from package: cdftools

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

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