Initially, the issue lies with the browser compatibility of this particular website, which can be described as less than ideal. In all honesty, it seems to stem more from a logical problem rather than a technical one. It appears that the height of each section has been set along with a designated scroll amount. This inevitably leads to discrepancies when zooming out, requiring adjustments in scroll amounts and section heights. One potential solution could involve adding padding to each section to adequately fill the screen height, subsequently adjusting the scrolling based on these new dimensions.
In my personal opinion, it may be more effective to rethink the proportions by scaling everything down to 90% of its current size rather than attempting to mask underlying issues. If the preference is for a 90% scale, then it should be created as such instead of simply appearing to be at that percentage.
Note: Originally intended as a brief comment, but ended up being somewhat of a rant...