Question: How many females use ZUK Z1 phones in the age group under 23?
SQL: SELECT COUNT(T1.device_id) FROM gender_age AS T1 INNER JOIN phone_brand_device_model2 AS T2 ON T1.device_id = T2.device_id WHERE T1.gender = 'F' AND T2.device_model = 'Z1' AND T1.`group` = 'F23-' AND T2.phone_brand = 'ZUK'