Yes it is legal to ship zoas. There is a slight risk though that a customs agent will open it and not be able to confirm it. Potentially then there could be delays and other headaches.
I think to Canada it's the same as shipping to the uk. There has to be no Lr on the frag. As said above if declared as zoas some customs agents won't know what is what and there might be delays etc. The best way for them is to be labelled ceramic aquatic decorations. Hope this helps!