you can't do it with camera in 2D

but you can use scale() once at the beginning, all the following is then scaled.
I can't see, why you don't want to use it.


see

https://forum.processing.org/topic/zoom-centered-on-mouse-coordinates-in-conjunction-with-zoom-centered-on-width-2-height-2

show your Code

You could use a damping so not jump to your scaling but go to it with factor 0.2 or so.

Greetings!

the only thing I know is this post
about pan and zoom

https://forum.processing.org/topic/zoom-centered-on-mouse-coordinates-in-conjunction-with-zoom-centered-on-width-2-height-2#25080000001641117