Development tools for Zephyr on STM32Workbench for Zephyr: VS Code extension to set up, build, flash and debug Zephyr applications on STM32.Devicetree manager: browse, edit and visualize Zephyr devicetree, STM32CubeMX-like for Zephyr.
You can specify for each project which compiler to use by modifying only compiler bin path (Project Properties > C/C++ Build > Settings > Tool Settings (Tab) > MCU Settings > Path)