Came out for no cool call on 2021 Heil AC/80% Furnace with 3 zones. Upon arrival customer let me know she has 2 downstairs tstats set to heat and upstairs to cool. Let her know zone system's can only either all heat or all cool, not both simultaneously. Customer now aware she can change temps but all 3 tstats must be set to heat or cool together. She let me know also tstat keeps shutting off after running for a bit then cycle repeats. Inspected system and found multiple issues. Firstly this is a 3ton system with three 10" supply ducts then one 8" and three 10" returns (also 10"bypass). With bypass closed and all 3 zones calling this is still not sufficient airflow, let alone for only 1 or 2 zones. Other main issue is she has single-stage heat and AC with 3 zones. With current ductwork this will never work properly. Recommend upgrading to variable speed equipment for proper zone control and balancing. Also found 10" bypass damper stuck closed. Set for .75in w/c of static pressure, even