By default this board will be built without accounting for pulpino-specific ISA. To account for them, edit zedboard_pulpino_defconfig and set CONFIG_RISCV_GENERIC_TOOLCHAIN=n.
However, in this case, a pulpino-specific toolchain should be use, by setting the following env variables, prior to compiling an application.
To setup the build system with the correct toolchain use:
export RISCV32_TOOLCHAIN_PATH=~/path/to/pulpino/toolchain export ZEPHYR_TOOLCHAIN_VARIANT=riscv32