I think that the Zootopia comic series from Dynamite Entertainment is a prequel to Zootopia 2 explaining how Nick and Judy became police detectives.

In Zootopia 2, Nick and Judy both appear as undercover police detectives, wearing normal clothes instead of police uniforms, so I think that the fifth and sixth comic issues of the Zootopia comic series from Dynamite Entertainment are going to reveal that Bogo gave Nick and Judy promotions to police detectives as a reward for solving the PB&J case.