sz80: 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/sz80 - from package: sdcc-ucsim

You may install the required package with command apt-get install {package}
Error in other languages:
sz80: bevel nie gevind nie
sz80: comandă negăsită
sz80: comando não encontrado
sz80: commande introuvable
sz80: command not found
sz80: käsku ei ole
sz80: không tìm thấy lệnh
sz80: komanda nerasta
sz80: Kommando nicht gefunden.
sz80: kommandot finns inte
sz80: komut yok
sz80: nie znaleziono polecenia
sz80: níor aimsíodh an t-ordú
sz80: no se encontró la orden
sz80: no s'ha trobat l'ordre
sz80: opdracht niet gevonden
sz80: parancs nem található
sz80: perintah tidak ditemukan
sz80: príkaz nenájdený
sz80: příkaz nenalezen
sz80: команда не найдена
sz80: командата не е открита
sz80: 命令找不到
sz80: コマンドが見つかりません