Zoho recently 11/15(ish) updated the software they use to render pdf's inside of zoho mail web.

#1 - Very slow rendering larger pdf's

#2 - Can not control Zoom location - zooms but no way to pan around

#3 - Early days was only printing first page of a pdf, not additional pages (Now fixed)

Not sure why Zoho changed the rendering method for PDF's  the previous setup worked fine.