Is it OK to mix and distribute data licensed under CC0 and Public Domain?

Question

I would like to create an style-unified collection of cartographic symbols - mainly for use with free SW like QGIS.

I would like to use (probably modify) some already prepared ones from various CC0 licensed sources like SJJB icons or Maki icons but also some from OpenClipart Library

Am I right if I think that I can freely mix and modify distributed content without need to cite sources for particular icons? I plan to keep the CC0 1.0 Universal (CC0 1.0) Public Domain Dedication license even for my original additional icons to not to restrict use in any way and I plan to add something like "Some icons are from source 1), some from source 2)" etc. - just to be fair.

Is it OK?

thanks

Answer 1

If they are licensed under CC0 it is impossible to infringe their copyright.

You have the same rights as if they were public domain due to age.