We have disabled the build system problem-matcher for C code, as it duplicates the IntelliSense errors, but does not update the errors as you edit. The problem-matcher can be reinstated by binding custom tasks to the build action, if preferred.
We have also silenced warnings in Zephyr's LOG_XXX macros by enabling the __CDT_PARSER__ define, which instructs IntelliSense to skip log macro parsing altogether.