Last year, Zendejas, 35 and in his 11th year in the league, made 18 of 23 field-goal attempts for the Rams, the 49ers' opponent Sunday, but was let go after the team drafted Steve McLaughlin.
In a shake-up of the San Francisco offensive line, Jesse Sapolu will move to center, replacing Bart Oates, and Kirk Scrafford comes off the bench to fill Sapolu's former spot at left guard.
The changes follow last Sunday's 18-17 loss at Indianapolis in which Steve Young was sacked a season-high six times.
Chicago Bear tight end Chris Gedney, who is also the punt snapper and holder, has lost 20 pounds and has been hospitalized again for another week of treatment for ulcerative colitis. Jay Leeuwenburg will take over the long snap duties, and either Todd Sauerbrun or Steve Walsh will hold for kicker Kevin Butler.