The good news is that I haven’t bricked my MacMini which still boots up in OS X El Capitan. I think that, subject to what people say within this forum, it is not going to be possible to run the Zorin OS on Apple Mac kit without someone doing some serious development work. Which is a pity.
I understand a user must use refind to install Linux on a Mac or Apple product.
I just did a search and this came up- a newer version of Ubuntu and a newer MiniMac, but I suspect the essentials are the same: