You're right, ZIS and ZIL is the same factory, which was born as AMO in 1916. ZIS ('Zavod Imeni Stalina' - 'Stalin Plant') was renamed in 1956 in favor of its former director and subsequently Minister of road transport and highways in USSR Ivan Likhachev and became ZIL ('Zavod Imeni Likhacheva' - 'Likhachev Plant'). You may remember when Khruschev came into power Stalin's cult of personality was dispelled.