Update SQL com Inner Join

UPDATE SZ4020
SET Z4_VEND1 = '999999'
FROM SZ4020
INNER JOIN SZ5020
ON SZ4020.Z4_NUMCTR = SZ5020.Z5_NUMCTR
WHERE Z4_CLIENTE BETWEEN '001385' AND '002621'

UPDATE SZ5020
SET Z5_GERCOM = '2'
FROM SZ5020
INNER JOIN SZ4020
ON SZ5020.Z5_NUMCTR = SZ4020.Z4_NUMCTR
WHERE Z4_CLIENTE BETWEEN '001385' AND '002621'

**********************Verificações *******************


Select * from SZ4020
WHERE Z4_VEND1 = ''

SELECT * FROM SZ4020
INNER JOIN SZ5020
ON SZ4020.Z4_NUMCTR = SZ5020.Z5_NUMCTR
WHERE Z4_CLIENTE BETWEEN '001385' AND '002621'

SELECT * FROM SZ5020