Not the same issue, but after the latest update, some staff here have noticed that if they open Excel and type in any cell, the cursor disappears and doesn't come back unless you reload Excel. If you just open Excel without editing a cell, it works fine!!
To fix this, I changed the setting for multiple displays to “Optimize for compatibility.” This fixed the cursor issue. I wonder if it might also resolve your zoom issue??
Might not make any difference for your issue, but it solved my equally odd issue with Excel this week.