Quartus: Error (12004): Port z does not exist in primitive x of instance y
You need to use sensible names for your modules, not really shortened ones.

tff is a primitive supplied with Quartus, so it is using the built in primitive, not your module. The primitive doesn't have a port named a, so you get an error.

The error message is quite specific about this. It tells you that the "primitive" doesn't have that port. If it was an issue with your module it would tell you the "module" doesn't have that port.