I'm not the biggest fan of the Zorin hexagon logo, particularly the small one in the top bar with the Mac OS layout. On the taskbar it looks OK but the it's a bit too angular and harsh when scaled down. I made a couple alternate ones that are more rounded that I think fit a little better with the default theme. There are 2 versions, a solid and an "inverted" one which can be copied into the Zorin Menu extension folder.
Backup the default icon first:
sudo cp zorin-icon-symbolic.svg zorin-icon-symbolic-orig.svg
Copy one of the alternates to the extension folder (assuming it is in your user Pictures folder):
sudo cp ~/Pictures/zorin-icon-symbolic-solid.svg zorin-icon-symbolic.svg
sudo cp ~/Pictures/zorin-icon-symbolic-inverted.svg zorin-icon-symbolic.svg
Alt + F2, type r, then Enter
Alternatively, you can use a different menu extension which often has options for a custom icon. Would be nice if the built-in Zorin menu had this as well.