This does not, although looking at the error it seems to be doing the right thing:
day_of_week = 'monday'
conn.execute(scheduled_jobs.update().where(and_(scheduled_jobs.c.zone == (zone_name),
                                     scheduled_jobs.c.zone_job == (zone_job))).values({f'scheduled_jobs.c.{day_of_week}': False}))

Trace:
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/sql/crud.py", line 179, in _get_crud_params
    % (", ".join("%s" % c for c in check))
sqlalchemy.exc.CompileError: Unconsumed column names: scheduled_jobs.c.monday

Nor does this work, and the trace is identical:
day_of_week = 'monday'
c_statement = f'scheduled_jobs.c.{day_of_week}'
conn.execute(scheduled_jobs.update().where(and_(scheduled_jobs.c.zone == (zone_name),
                                     scheduled_jobs.c.zone_job == (zone_job))).values({c_statement': False}))


Trace:
File "/usr/local/lib/python3.7/dist-packages/sqlalchemy/sql/crud.py", line 179, in _get_crud_params
    % (", ".join("%s" % c for c in check))
sqlalchemy.exc.CompileError: Unconsumed column names: scheduled_jobs.c.monday