no really how the multiple form is made??
There seems to be a lot of different patterns with some exceptions but from what I'm seeing most of them are either "-a", "-i" or "-y" endings
How do you pronounce "zwie"? I thought there should be an "e" sound after the palatalized "v", but I hear an "ee" sound.
it's normal Polish "e". I think pronunciation guide compared it to e in bed
Is this a completely irregular plural. I can find no example of this ending in my list of Plurals (Swan: Polish verbs and essentials of grammar)
Not only the plural, its complete declension is irregular. There are no more than just a couple dozen of such neuter nouns ending in -ę. Except for zwierzę, they are not very common, though.