If you are only loking for Zo's then Canadian Reef is the place to go.
However there are a number of stores in the Toronto Area that do have smaller selections of Zo's as well as other corals and fish.
http://www.aquariumdepot.com/ (Brampton)
http://www.oakvillereefgallery.com/ (Mississauga)
http://www.canadianreef.com/ (Oakville)