I haven't used the email services of Yandex before but I do use the email services of zoho for an extra email account. I have used many different email services and the one that I would compare it closely to is mail.com.
They are not a top-tier email provider IMO but still good if you need another email address. Their spam filter is not very good but acceptable.
Overall they are ok but I prefer the email services of Google or Microsoft.
I'm using Zoho for my business mailboxes, and if you want to use a single custom domain, it's a very good solution. But if you want to use several custom domains, it can be pretty expensive with zoho.
My previous organisation had some experience with Zoho. I personally find Zoho more reliable and trusty for my uses.
My recommendation would be to use Zoho over Yandex if you are looking for business usage.If you need to grab more accounts, it might be better to use Yandex.
I mainly use Gmail for my own individual freelance work at the moment though.
I have heard about Yandex, however, I have never used its email service or search engine service. I have never heard about Zoho. Since I have never used Yandex or zoho, I cannt say which email service is better. However, I did a quick search and discovered that yandex is very popular with Russians. It has 65 percent market share in Russia.