Irish passport holder as a tourist in Canada. I wish to apply for a Z visa.

Hello,
I hold an Irish passport and I am currently in Alberta as a tourist. My tourist type for Canada ends in Oct´14. I will then travel to the USA for a holiday and then I wish to travel on a Z type to China in Nov´14. Can I apply for a Z type from within Canada (Calgary Chinese Embassy) or do I need to apply via the Dublin Embassy? If I can apply from within Canada, and I get the Z type, I won´t be flying directly from Canada to China (I will be flying from the USA);will this cause problems?
Many thanks!
Tamsin