Firstly, while it may be easier to call them 'accents', they are separate letters with separate pronunciation.
ż (Z with a dot) is roughly English zh (which of course is not a common sound).
ç (C-cedilla) is not a Polish letter, it's Portuguese (and some other languages).
ć is probably what you meant. I'd say that it's a palatalized T. The palatalized sounds are very difficult for Polish learners.
ę is roughly 'eu'. Imagine the Spanish pronunciation of "Europa".
ą is roughly 'ou'. The vowel sound in "rose".