How to set up calculated fields in Google Data Studio?

Question

Regular Expressions

You need to create an indicator in which the field and expression are:
1. “Campaign”,*(NAME_COUNTRY).*
2. REGEXP_MATCH(Source or channel, '.*(google / cpc).*') Figured
out number 1:
CASE
WHEN REGEXP_MATCH(Campaign,'.*(Russia|England|Germany|France).*') THEN “EUROPE”
WHEN REGEXP_MATCH(Campaign,'.*(US).*') THEN “NORTH. AMERICA”
ELSE “Others”
END
And here is how to add condition number 2…
UPD #1: I don't know how to nest another CASE
UPD #2: I tried to add an AND operator like this:
CASE
WHEN REGEXP_MATCH(Campaign,'.*(russia| germany|france|england).*') AND REGEXP_MATCH(Source or channel,'.*(google / cpc).*') THEN “EUROPE”
WHEN REGEXP_MATCH(Campaign,'.*(us).*') AND REGEXP_MATCH(Source or feed,'.*(google / cpc).*') AMERICA”
ELSE “Other”
END
With this option, the data in the “Other” category got out
And if you apply a filter in the report on the traffic source I need, everything is OK
How to be?)))
Thank you in advance