Ref: topic from @davidgPGADA (ACC general discussion forum)
An improved zoom when viewing sheets through the mobile app for ACC Build.
For example, when viewing a sheet through the web browser, you can zoom in a great deal further to read very fine print tags. Though when viewing that same sheet on the mobile app, the zoom functionality is limited so you can't see the same detail.
Autodesk replied to this topic and suggested to use/turn on the built in Zoom option on a tablet.
This is an option you can turn on in both tablets and mobile devices.
When this feature is turned on it creates an extra window you can use to zoom onto the sheet.
But this extra zoom window on the screen makes it difficult to use the mark-up function.
On a computer or a laptop there is no zoom issue when zooming onto a sheet and making issues or mark-up.
So, it seems that this issue only applies to tablets or mobile devices.
I hope there will be a solution for sheet zooming in the ACC mobile app.