Albert Barnes Commentary Ezra 4:2

"then they drew near to Zerubbabel, and to the heads of fathers` [houses], and said unto them, Let us build with you; for we seek your God, as ye do; and we sacrifice unto him since the days of Esar-haddon king of Assyria, who brought us up hither." — Ezra 4:2 (ASV)

Compare (2 Kings 17:24–28) notes.

Since the days - Esarhaddon reigned from 681-668 B.C. Thus, the Samaritans speak of what had taken place at least 130 years previously.

There appear to have been at least three colonizations of Samaria by the Assyrian kings. The first is mentioned in (2 Kings 17:24).

Later in his reign Sargon added to these first settlers an Arabian element. Some 30 or 40 years afterward, Esarhaddon, his grandson, largely augmented the population by colonists drawn especially from the southeast parts of the Empire (Ezra 4:10).

Thus, the later Samaritans were an exceedingly mixed race.