Lamb's deal is worth $21 million over three seasons, a person familiar with the situation told The Associated Press. The person spoke on condition of anonymity because the team doesn't disclose contract details.
Lamb, a fourth-year pro, was acquired in a June 25 trade after spending three seasons in Oklahoma City. He was the 12th overall pick in the 2012 draft by the Houston Rockets.
Lamb has career averages of 7.0 points, 2.1 rebounds and 1.1 assists in 150 games. He is a 35 percent 3-point shooter, and coach Steve Clifford has said he likes what Lamb brings to the team.
Zeller opened this season with the second team, but has started in the past. He was the fourth pick in the 2013 draft.
The 7-foot Zeller is averaging 6.7 points, 5.0 rebounds and 1.3 assists over 147 career games, including 48 starts.
The Hornets are 0-3 heading into Tuesday night's game against Chicago.