I have had a similar problem with another car, but could just as easy happen to a Zed.
The master cylinder builds up crud inthe cylinder bore over time. If you rebuild the brakes without doing the MC you can have problems withthe master cylinder. The piston get stuck when they got all the way to the bottom of travel and stay there. You don't notice because you are pumping brakes with a vacuum less booster. It just feels harder and different than normal. This could be your problem.
Its also not a good idea to run it with a "dirty" mc. It will probably fail soon after bleeding because the rubber cups are now most likely damaged by the pitting and grime in the bore section that was normally not wiped clean by the rubber cups.
Good luck
Chas
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