Legally, you should only download or compress ROMs for games that you physically own. You can even use desktop tools like to compress your own backup .bin / .cue files into .chd files manually, saving space on your hard drive legally and safely.
Essential, smooth performance in a tiny package. psx games highly compressed
Do you have any you want to combine?
In the "ISO file" dropdowns, select Disc 1, Disc 2, Disc 3, and Disc 4 in their respective slots. Set Output: Choose your destination folder. Legally, you should only download or compress ROMs