Learn Farsi: من لباس‌ها را در یک کیسه ضد بید گذاشتم.

The word zedd means opposite or against. When connected to a noun using the ezāfe (the -e sound), it acts just like the English prefix anti- or the suffix -proof. It is highly productive! Just like zed-e bid (anti-moth), you can easily create adjectives like zed-e âb (waterproof) or zed-e yakh (antifreeze).

How is the word kise (bag) grammatically connected to zed-e bid in spoken Farsi?

They are connected by another ezāfe. Because kise ends in a silent 'h' (which produces an 'e' vowel sound), it requires the -ye form to link to its modifier. Therefore, you pronounce the entire noun phrase as kise-ye zedd-e bid.

Does bid mean bug in general, or is it specific to moths?

bid specifically refers to a moth, and in everyday language, usually the kind of moth that eats clothes or carpets. If you wanted to refer to an anti-bug or insect-repellent bag in a general sense, you would use the word for insect and say zed-e hashare.

I sometimes mix up where to place râ in longer sentences. Why does it go right after lebâs-hâ here?

The object marker râ must immediately follow the specific direct object of the verb. In this sentence, the action of putting directly happens to the clothes (lebâs-hâ). The rest of the sentence () is just a prepositional phrase showing where they were put, so it stands on its own after the object and its marker.