slingstones: In ancient battles, large stones were thrown at defenders on city walls and launched at people inside. The Maccabees' victory over the Hellenistic Seleucids in the 100s BC might have partly fulfilled Zechariah’s prophecy of Israel defeating the Greeks (see 1 Maccabees 3:16–24; 4:6–16; 7:40–50).
they will be filled … drenched: When the Lord sends his armies against the Greeks, there will be a lot of bloodshed.
like sprinkling bowls: Ceremonial sprinkling bowls filled with animal blood were used in sacrifice rituals. This image suggests that defeating the Lord’s enemies is, in some way, an offering to him (see Exodus 24:6; Leviticus 1:5; 16:18).