Beware that ż has a "zh" sound (as in "measure"), while ź is a palatalized form of "z".
There is no palatalized Z /zʲ/ in Polish or English. Ź is /ʒ/ Just like the Enɡlish "pleaʒure." The Ż sound /ʐ/ doesn't exist in English but is also approximated by "zh" (/ʒ/) in English, so the two do not exist as separate phonemes in English. It takes a trained English ear to hear and understand the difference, not by trying to explain it with English words as examples. All English examples of Polish Ż are actually closer to Polish Ź.
Ok, so I know the rules for forming plurals have not been discussed yet (and in fact I am away ahead of here and still no sign of plurals being discussed), however I am using a grammar book to try and understand declension.
So here we have nominative plural. This word although masc. declines like fem. because it ends with "a". My book says...
"Here is the short description for forming the nominative plural of nouns: Neuter nouns have -a, hard-stem masculine and feminine nouns have -y/-i, and soft-stem masculine and feminine nouns have -e. In masculine personal nouns, the stem consonant softens before -y/-i."
Swan, Oscar (2008-10-12). Polish Verbs Essentials of Grammar, Second Edition (Verbs and Essentials of Grammar Series) (Kindle Locations 536-538). McGraw-Hill Education. Kindle Edition.
So we have here a hardstem fem. (or even if its masc. the rules are the same) word, and the ending is therefore "y" or "i". BUT "-i is (ONLY) used after k and g" (ibid.)
So why do we have "i" here and not "y"? Or is this an irregular plural?
This rule applies mainly to inanimate objects, I believe. Rules of plurals differ between inanimate and animate. For example:
The plural of "Polak" is "polacy". Similarly, the plural of "kułak" is "kułacy". That's because both of those nouns refer to people.
However, the plural of an analogous word "kołpak" is "kołpaki", not "kołpacy", because it refers to an item.
(an exception is "chłopak" - both "chłopacy" and "chłopaki" are correct)
Basically, there is a lot of explaining to do. Look it up on the Internet or pick up another book :)
Mężczyzna ( man, male ) • Mężczyźni ( men ) Collective feminine Noun until 17th century, From mąż (man) + -czyzna (collective suffix), from Proto-Slavic mǫžь < Proto-Slavic mon-g- < Proto-Indo-European man-
Mąż ( husband, man, male, manliness - Noun ) • -czyzna ( abstract quality, state of being, possession - Suffix ) • czy ( is yes/no? - Particle | if, whether, or - Conjunction ) • Zna ( know - Verb 3rd Person Singular Present ) • Znać ( to know - Verb )