I had a look at the HP site, and this printer is supposed to be PCL3 GUI based - see:

http://support.hp.com/gb-en/product/HP-LaserJet-Pro-CP1025nw-Color-Printer/4052955/model/4052971/document/c02467384

Though I could not find any mention of it being PostScript enabled on the HP pages, but sometimes even their descriptions of their own printers falls far short (not the standard they used to be associated with) and gives an incomplete description & specification thesedays.

However, you own the printer, and I feel sure you know what it is capable of, or not, as the case may be.

I am not aware that zjstream is on the current todo list for MorphOS printing, as I have not seen it mentioned.

I bought an older HP 2500 CLJ as that printer has a legacy 36 pin Centronics, also a USB interface, additionally it has an Ethernet card fitted, so I can choose several options to print from, and it works with my Classic Amiga system as well as my MorphOS, Mac & Windows systems, and allows 600 x 600 dpi colour printing which is what you printer seems to offer as well.