What bother you? "rz" is pronounced like "ż", final "ę" can be denasalized so it can be pronounced similarly to "e"
what part you don't understand ? rz? ę? ę sounds like e (polish one) at the and of word. nouns in Nominative end with ę - and you hear that ę in other cases zwierzęcia....zwierzęta rz sounds exactly like ż and while there are sometimes rules for which is when I don't recall any that applies to zwierzę
Because "zwierzę" is actually the nominative form of the word. It's not an accusative feminine noun.
True. But some words just look like that, although there are not many of them. Also for example "źrebię" (a foal) and "cielę" (a calf).
A person isn't exactly an equivalent of "człowiek". If you consider science-fiction races, or fantasy races, all sentient beings should be considered 'persons', but they're aren't human.