Answered by Shaykh Faraz Rabbani
Can one wear khuff on one foot only and wipe over it while doing regular wudu on the other foot? This is just a question about validity of the wudu, not really touching on the fact that it is rather strange to wear the khuff on one foot alone.
Answer:
Assalamu alaikum wa rahmatullah,
No, it is not valid to wipe on footgear on one foot and to wash the other. [Zayla`i, Tabyin; Shurunbulali, Maraqi al-Falah]
And Allah alone gives success.
Faraz Rabbani
ولا تجتمع الوظيفتان في الرجلين (تبيين الحقائق شرح الكنز)
(ولا يجمع بينهما ) الغسل مع المسح على الخف في إحدى الرجلين
Jazakum Allah khayr.
And Allah alone gives success.