I have a column of concatenated text, and would like to add another column
that "deletes" certain strings of characters if it is found in the
concatenated column.
For example, if text strings of "xx" or "yy" are found, I want those
characters to be deleted. So, WWXX would just show as WW; YYZZ would just
show as ZZ.

I found I can use the substitute function to search for just one string:
=SUBSTITUTE(A2,"XX,""). Can I modify this formula to perform the
replacement if XX or YY is found?