Use Dolphin’s command line converter:

dolphin-tool convert -i game.rvz -o game.iso -f iso

Converting RVZ to ISO Using Universal Patching Data (UPD): Methodology and Implementation

Dolphin has a built-in conversion tool – no extra software needed.

Before clicking "download," you need to understand what you are working with.

Many users searching "convert rvz to iso upd" actually want to play on a real Wii via USB Loader GX. In that case, you don't want ISO; you want WBFS (still requires an intermediate ISO).

Tool: Wii Backup Fusion (Updated 2024-2025 versions).