We Currently use windows PC and a ZP450 using the default manufacturer driver for our packing slips.
The labels we use are standard 6x4 on perforated shipping label slips, the packing slip that we tested were both custom made packing slips or standard default packing slips.
We have it set-up where all shipping labels print with packing slips.
When we generate labels in batches or simply purchase a single label within an order page, we found that shipstation occasionally (more frequently) prints blurry text on the packing slips and shipping labels. Regardless how many times we configure the printer on the print document that we download at first generation.
What we found out is in those orders if we bruteforce shipstation to regenerate the labels and print, the print comes out as intended without any blur.
Is this because of a back-end programming that shipstation needs to work on?
Shipstation support is classic at ignoring support issues.
Good luck with them.
I have the same config that you do, and the same printer.
That printer has 203 as its greatest DPI setting.
Even so, I notice our lables come out crisper, when we set the DPI to 300.
Setting our print speed has no effect.
Setting our print driver to print in "color", makes the text even better for some reason.