[arensb]

I don't see a way to search by multiple columns. But what you can do is build an intermediate column #author_pub, whose value is the author and publisher, separated by a slash. Create it in Settings > Add your own columns:

Lookup name: author_pub
Column heading: Author + Publisher
Column type: Column built from other columns
Template: {authors}/{publisher}

Then you can look for books where the #author_pub column has some value, followed by a slash, followed by the first value:

#author_pub:"~^(.*)/\1$"

Where "#author_pub:" means "we're going to be searching the author_pub column.
The double quotes just group things together.
"~" means "we're doing a regular expression search, not an ordinary string search.
"^" means "beginning of string" and "$" means "end of string". So we're looking for "(.*)/\1" and nothing else. Basically, we don't want to do a substring search: you don't want to look for books where the author is "Smith" and the publisher is "Smith and Jones", or where the author is "Jones and Smith", and the publisher is "Smith".
".*" means "any number of characters", and the parentheses around that basically mean "remember this for later". "\1" means "the first parenthesized expression".
Finally, the slash "/" is just a slash, because that's what separates the author from the publisher in this custom column.

Putting all that together, we're constructed a custom column with the author and publisher, separated by a slash. And then we search that column for some sequence of characters starting at the beginning, then a slash, and then the same sequence of characters as before, and finally the end of the string.

You can then select all books in that result, and use the Bulk Metadata editor to replace the publisher.