Abarim Publications' online Biblical Hebrew Dictionary
Scholars identify two separate roots of the form זנח (znh), but their meanings are so closely related that one may doubt whether Hebrew scribes and audiences considered them as separate:
The verb זנח (zanah I) means to reject and that commonly because of a strong dislike or disapproval, and that mostly by the Lord.
Jeroboam rejected the Levites (2 Chronicles 11:14), and Ahaz the sacred utensils (2 Chronicles 29:19). Israel rejects the good (Hosea 8:3), but YHWH rejects Samaria's calf (Hosea 8:5). He also rejects the Psalmist (Psalm 43:2), the nation (Psalm 60:1), his altar (Lamentations 2:7), even his anointed (Psalm 89:38), but will he reject forever? (Psalm 77:7).
No, declares Zechariah, because the houses of Judah and Joseph will be as if he had not rejected them (Zechariah 10:6).
The verb זנח (zanah II) means to stink, and it occurs only once, in Isaiah 19:6, where the Lord deals with Egypt, makes the sea dry up and the rivers stink.