Ice Station Zebra Associates is the name of a holding company used by Saul Goodman for tax evasion. In the episode "Abiquiú", Skyler White decides to intervene in Saul and Walter White's money laundering plans in part because she was unimpressed when Saul presented her with a check from Ice Station Zebra Associates.
Ice Station Zebra Associates is also seen in small print in the television commercials for Saul's law firm.
In the Better Call Saul episode "Bali Ha'i," Kim and Jimmy run a con and convince a stranger at a bar to write a check for $10,000 to invest in their start-up tech company. The check, later shown at Kim's apartment, is written to Ice Station Zebra Associates.
"Ice Station Zebra" is itself a 1963 Cold War intrigue novel, adapted in 1968 as a better-known film starring Rock Hudson and Ernest Borgnine. The movie itself appears in "Amarillo", watched by Saul (James McGill at the time) and Kim Wexler .