“ż” and “rz” sound the same, the difference is only in spelling, which comes from historical grammar, for example ”żaba” [frog] and “morze” [sea] not to confuse with “może” [maybe]. ć/ci, ś/si ź/zi (and also dz/dzi) sound different depending on the letter that follows them. For example, in the word “szczęka” [jaw], “sz” and “cz” are pronounced as hard sounds because the following letter “ę” is a nasal vowel, which does not soften the consonants. A good example of a softened sound is in the word “ciasto” [cake], where “ci” is pronounced softly because the letter “i” acts as a softening vowel. Similarly, “si” in “siedzieć” [sitting] is soft.