Mainly yes - only real problem you might have is that the ZX300 (or maybe all Sony Daps in general) does not like the image if its format is a progressive jpeg (compressed)... if that happens (your tags have a progressive JPEG image), the ZX300 won't display it.
Easy fix, if you have a Windows computer and not a lot of duds (I had to do that, myself) : scroll your album list in the DAP, jot down what album art is not showing, open files in MP3tag, select songs, copy the album art, open the Paint program and paste the art in it. Then copy the image in Paint, go back to MP3tag, remove original cover, paste new cover and save the updated tags... you'll notice that the size has increased (it's not compressed any more
). And there's no need to save image in paint, just copy/paste does the trick.
Had to do that on about 20 albums, on my 400 GB micro SD card, but YMMV, obviously... if you're lucky, all of your art will be fine, or you'll not have a lot to do... if one is very unlucky and everything is in progressive jpegs, that's gonna be a giant PITA with my method, unfortunately. Maybe somebody else knows some other program which can take care of that automatically (I don't, though).