Go further. Get rid of all zoning that’s unrelated to pollution of some kind or strictly a safety issue. Why is the government involved in whether I can run a business from my home? Why is the government responsible for controlling where businesses might be located instead of the free market controlling that aspect more dynamically?
The reasonable justification is government builds public infrastructure like schools, highways, and subways based on assumptions about use and population density. It’s much harder and more expensive to have reasonable infrastructure if you can’t make accurate predictions. The de facto justification is indirect negative externalities exist like traffic congestion. Also known as F U I got mine.
With uses segregated, the "reasonable" argument does not make sense to me: infrastructure will have to be maximized because there will be big migrations of people based on normal use times like going to work. You need twice as much parking, twice as much freeway throughput.