يَأْكُلُونَ is a third-person masculine-plural present-tense verb: “they eat.” In بِأَلْسِنَتِهِمْ, بِـ means “by/with,” while هِمْ means “their.” أَلْسِنَةٌ is the plural of لِسَانٌ, tongue.
كَمَا تَأْكُلُ الْبَقَرَةُ بِأَلْسِنَتِهَا uses كَمَا to introduce comparison; هَا refers to the cow.
The image links a bodily action to an ethical misuse of language: making speech an instrument of greed instead of truth.