For Zhdanov, you play as Komi, a warlord state in Russia. Voznesensky and the Democratic Coalition are in charge at first, but you can get Zhdanov to power by basically making decisions that boost his faction of the Communists Party. If you want an idea of how politics in Komi work and what getting him in charge is like, you can check out
this unfinished playthrough.
Konev is a potential Soviet leader in Thousand- Week Reich, which is a separate mod. To play him, pick the Soviet Union and when Beria dies, you basically pick choices during the subsequent Communist Party leadership debate that favour Konev.