This simple script will allow you to open all your znc bouncers that you own on mIRC startup.
Add the script in remote.ini and change it with your znc infos.

If you have more then three znc's just multiply the ".server -m your-ip +port user/network:pass -i nickname"

Enjoy!

; BEGIN

on *:START:{
  .server your-ip +port user/network:pass -i nickname
  .server -m your-ip +port user/network:pass -i nickname
  .server -m your-ip +port user/network:pass -i nickname
}

; END