"This market changes quickly."
Translation:Ten rynek szybko się zmienia.
Well, those are quite different issues. Let's see:
zmieniać = to change (something), infinitive, imperfective
rozmienić = to change (money, for example from 20 zł banknote to two 10 zł banknotes, or to coins), infinitive, perfective
zamówić = to order (on eBay, in the restaurant, etc.), infinitive, perfective
zamawiać = the same, but imperfective
zamkniemy = we will close, Future Simple
zamykamy = we are closing, Present Continuous (may be used in the future meaning)