Can I mix Calcium Hypochlorite with Benomyl imidazole?

I have no idea but regular spraying with diluted bleach will keep algae and mildew away without the need for a chemistry degree. LOL
On what and where is this mysterious algae and mildew problem occurring, is it indoors or outdoors?

That is a clever idea. I do not know if the Calcium hypochlorite will break down the BI. In your topics listing you mention using it on sandstone. I’d try just the bleach first and see what happens.

I would do bleach first to clean, then the BI to prevent future growth. You never know what would happen if you mixed them together first.

Vinegar kills and sort of melts mildew and mold. No idea what would clean algae off of something.