GMXRC.zsh: 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 CentOS possible default full paths are:

/usr/bin/GMXRC.zsh - from package: gromacs-zsh

You may install the required package with command yum install {package}

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