Both are adequate. Both are based on Ubuntu. The biggest difference is going to be the interface.

Zorin has a Gnome-ish interface. If you pay a few extra bucks, you can customize it to make it function like Mac or Windows or Ubuntu, etc. in one click.

Mint has a (in my opinion) much less modern interface that I don't like. But it's also, I believe, the single most popular Linux distro so there will be endless amounts of community support for it.