Addl evidence about Strzok being CIA, in addition to this week's Big League Politics articles.
https://www.intellihub.com/a-sheep-dipped-peter-strzok-works-for-both-the-fbi-and-cia-documents-reveal/
An unclassified document printed on FBI letterhead dated January 20, 2016, which contains the subject line “Supplemental Classification Review and Determination” was addressed to the Bureau of National Security’s Assistant Secretary Gregory B. Starr from Peter Strzok who is listed as “Section Chief” of the “Counterespionage Section” in reference to Strzok’s CIA post. Keep in mind, this is not an FBI post as Strzok’s position at the FBI is “Deputy Assistant Director Counterintelligence Division” not “Section Chief” which is a CIA post.
The site has a screenshot of the letter.