cdfzonalmean: command not found

Have You tried accessing the binary with the full path?

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/cdfzonalmean - from package: cdftools

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