favicon keeps changing! very annoying!

favicon keeps changing! very annoying!

Hello,
it appears that the favicon for Zoho Invoice keeps changing. I've seen 3 different favicons in my browser over the past few weeks. It's really quite annoying, as I'm looking for Zoho, thinking I can't find it, until I realize that the favicon has changed again.

Please choose one, and stick with it! Otherwise, there's not point in using a favicon at all.
Thank you