зі- - Wikiwand

Derives from multiple Proto-Slavic prefixes: *jьz-, *sъ(n)- and *vъz-. For details see з- (z-)

зі- • (zi-)

Alternative form of з- (z-) used before: с, з:
1. attached to imperfective verbs to form the perfective aspect
  ‎зі- (zi-) + ‎ста́вити impf (stávyty, “to put”) → ‎зіста́вити pf (zistávyty, “to put together, to compare”)
  
  ‎зі- (zi-) + ‎зна́ти impf (znáty, “to know”) → ‎зізнатися pf (ziznatysja, “to confess”)
(used with verbs) together (indicates bringing together literally or abstractly)
‎зі- (zi-) + ‎бра́ти impf (bráty, “to take”) → ‎зібра́ти pf (zibráty, “to collect, to gather, to assemble”)
(used with verbs) down and/or up (indicates up-, downward movement)
‎зі- (zi-) + ‎йти́ impf (jtý, “to go”) → ‎зійти́ pf (zijtý, “to go up, to ascend; to go down, to descend”)