The only 2 prograns that can open .kra are Krita and ReveriePaint afaik.

As for .zip, all i am aware of are comic book readers. Those support .cbz and other renamed archives. I personally just use file manager (MiXplorer in my case) for this. You may try to submit a feature request to Aves.

I consider st a great choice when using i3 or dwm. Customizing it takes time, but RAM usage is what I usually check and in case of st it is comically small.