zcov-merge: 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/share/doc/mongrel2-core/examples/zcov/bin/zcov-merge - from package: mongrel2-core

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

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