Thanks for the comment :)
First, Don’t forget that Paper is a sketchbook app, not a drawing - painting app
Paper simulate the reals conditions of using a sketchbook… So, in real you cannot zoom ;)
Just imagine that you have a real A5 sketchbook.
The avantages are that you have sketching tools at hands and an infinite numbers of pages, so don’t be affraid by the white page! Draw!
If you want to do more details drawings you can make a quick sketch in Paper and import it in a drawing - painting app as Procreate, Sketchbook pro… There is a zoom and specificals tools for it.
Hoping help you.
Ps: sorry for my english :s