Changelog

To change the mode in zen-iosched
echo 1 > /sys/block/<devices>/queue/iosched/mode # Gaming
echo 2 > /sys/block/<devices>/queue/iosched/mode # Battery
echo 0 > /sys/block/<devices>/queue/iosched/mode # Normal

Normal Mode:

echo 0 > /sys/block/mmcblk0/queue/iosched/mode
echo 0 > /sys/block/sda/queue/iosched/mode
echo 0 > /sys/block/sdb/queue/iosched/mode
echo 0 > /sys/block/sdc/queue/iosched/mode
echo 0 > /sys/block/sdd/queue/iosched/mode
echo 0 > /sys/block/sde/queue/iosched/mode
echo 0 > /sys/block/sdf/queue/iosched/mode

Gaming Mode:

echo 1 > /sys/block/mmcblk0/queue/iosched/mode
echo 1 > /sys/block/sda/queue/iosched/mode
echo 1 > /sys/block/sdb/queue/iosched/mode
echo 1 > /sys/block/sdc/queue/iosched/mode
echo 1 > /sys/block/sdd/queue/iosched/mode
echo 1 > /sys/block/sde/queue/iosched/mode
echo 1 > /sys/block/sdf/queue/iosched/mode

Battery Mode:

echo 2 > /sys/block/mmcblk0/queue/iosched/mode
echo 2 > /sys/block/sda/queue/iosched/mode
echo 2 > /sys/block/sdb/queue/iosched/mode
echo 2 > /sys/block/sdc/queue/iosched/mode
echo 2 > /sys/block/sdd/queue/iosched/mode
echo 2 > /sys/block/sde/queue/iosched/mode
echo 2 > /sys/block/sdf/queue/iosched/mode

you can use that command in termux, in file manager also possible, in the FKM apk you can also use Costume Tunables