If you have your pc hooked up to the tv, run your computer’s resolution to match your tv’s maximum res (IE. mine is 1920 x 1080), then run zsnes at the same resolution.
Even then though, it will look horribly horribly pixelated (that was the nice part about old TVs, their grainy, fuzziness smoothed out those pixels). I used hq4x, it smooths out everything without looking fake and cruddy. If you really want it to look like what you remember from your childhood I know there’s Atari emulators that actually recreate the fuzz, you could try to find something like that for ZSNES.
What I usually do with Kawaks is set it so that it displays the resolution in VGA and I have some video filters on. This allows for zero lag and good looks. Not sure about ZSNES and its options though.
You can try putting on scanlines. It looks weird but it fakes doubling the resolution of the original. Other than that just mess around with the different filters until you find something you like.