On my computer, Zero-width space shows as a box with most screen fonts, and is quite wide with Adobe "Pro" postscript fonts. It can be used with Segoe UI, which wouldn't be my choice as I dislike cleartype.
The pair $char(8203) $char(65279) can indeed be used to get invisible output with Segoe UI.
$puts(crc,$crc32(%catalogue%))$puts(crt,$replace($select($add($mod($div($get(crc),256),16),1),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110,1111)$select($add($mod($div($get(crc),16),16),1),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110,1111)$select($add($mod($get(crc),16),1),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110,1111),0,$char(8203),1,$char(65279)))%composer%|%catalogue%$get(crt)|%album% '['%conductor%']' '['%mediatype%-%discnumber%']'|[%tracknumber%. ]%title%