From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Zeph'athah. (Watch-Tower). The Valley Of Zephathah . The spot in which Asa joined battle with Zerah, the Ethiopian.  2 Chronicles 14:10 only.

Morrish Bible Dictionary [2]

The valley in which the battle with Zerah was fought.  2 Chronicles 14:10 . Identified with Wady Safieh, 31 37' N, 34 55' E .

Hastings' Dictionary of the Bible [3]

ZEPHATHAH . An unknown locality named only (if the text is correct) in   2 Chronicles 14:10 (9).

American Tract Society Bible Dictionary [4]

A valley near Mareshah, south-west of Jerusalem, where Asa defeated Zerah the Cushite,  2 Chronicles 14:10 .

Holman Bible Dictionary [5]

 2 Chronicles 14:10 Zaphon Mareshah

Easton's Bible Dictionary [6]

 2 Chronicles 14:9-13

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [7]

(Heb. Tsepha'thah, צְפָתָה , Watchtower; Sept. Κατὰ Βοῤᾶν ; Josephus, Σαφθά , Ant. 8: 12,1; Vulg. Sephata ) , the name of a valley ( גֵּאי ) where Asa joined battle with Zerah the Ethiopian ( 2 Chronicles 14:10). It was "at," or rather "belonging to," Mareshah ( לְמָרֵשָׁה ; Josephus, Οὐκ Ἄπωθεν ) . This would seem to exclude the possibility of its being, as suggested by Robinson ( Bibl. Res.2, 31), at Teles-Safieh, which is not less than eight miles from Marash, the modern representative of Mareshah. There is a deep valley, which runs past the latter place down to, Beit Jibrin, and thence into the plain of Philistia. This, perhaps, may be the valley of Zephathah (Porter, Handbook, p. 258). Some, however, understand the name Zephathah to be only thatof Zepihath (q.v.), with ה directive, and render it "the valley towards Zephath."

Kitto's Popular Cyclopedia of Biblial Literature [8]

Zeph´athah, a valley at Mareshah, in the tribe of Judah (), where Asa defeated Zerah the Cushite. Mareshah was near Eleutheropolis, and Robinson thinks the valley may have been the broad wady which comes down from Beit Jibrin (Eleutheropolis) towards Tell es-Saifeh; in which last name a trace of Zephathah may perhaps be recognized.