Not sure what a zester is. But, I think that what “they” say about citrus fruits in compost should have been researched by the commentators. Also, you perceive pith as not being distateful. Since some people do, make your comment as, ‘in my opinion,’ so we know it’s not necessarily a scientific fact.
As far as other wonderful uses:
Try them to freshen in your garbage disposal. That’s not a culinary use, buy does handle onion, garlic, and coffee ground smell for us non-composters. I sometimes has to soften up first.

Like this article. Just a comment on a comment. You should NEVER assume people know what you know. When giving advice/instruction/direction be as specifically detailed as possible (like the 1 tsp of zest = 1 tsp of powder). I think indicating IN the directions to use ONLY organic oranges is an appropriate recommendation, not a criticism (we can’t think of everything; comment forums helps)..

You should use only the rind and not the pith when making this.

Well you are supposed to know to use organic fruits.

Use organic produce or fruit from someone’s personal fruit tree.

I think I used mine for six months and it was still good.