(1) The jurisprudential rulings of four Imams are not sects rather they are the differences emerged as a result of Shariah proofs which are not nefarious in the eyes of Shariah rather they are source of mercy for the Ummah as per the Hadith. The person who does not have the ability of Ijtihad it becomes necessary for him to follow any imam out of the four as he cannot practice Shariah without Taqleed. It is necessary to follow Shariah for salvation in hereafter. And it is must to follow one of the four imam in all the rulings. It is in no way lawful to follow Imam Abu Hanifa (رحمةالله) in some rulings while Imam Malik, Imam Shafai or Imam Ahmad (رحمهم الله) in some rulings as it is talfiq (contrivance) which is haram as per the majority of Ummah. It should be noted that four Imams do not differ in all the rulings. They differ only in the rulings regarding which the Quran and Hadith are apparently clashing or they have more than one meaning or there is no explicit ayat or hadith regarding them.
(2) There is a detailed fatwa about Dr. Zakir Naik on the website of Darul Uloom Deoband, you should see it, you will know the reality of Dr. Zakir Naik. Who is Muhamamd Salah of Huda TV? I do not know him. If you mean by him Al Huda International (New Name: Al-Noor International) headed by Dr. Farhat Hashmi then all the Ahl Haq Ulama of Pakistan agree that she is deviant. (For details read the book “Maghribi Jiddat Pasandi Aur Al-Huda International, Maqasid, Azaim Andeshe” you may download it from www.ahlehaq.com website). As far as the Salafi i.e. Ghair Muqallidin are concerned, they are deviant and out of Ahl Sunnah Al-Jamah because they refuse the argumentation of Qiyas and Ijma of Ummah. The commentary of the holy Quran and Hadith which they present against the Sahaba, Tabiyeen and other Akabirin Ummah is not acceptable as per the Ahl Sunnah Al Jamah. Hence it is not lawful to trust Ghair Muqallid Ulama as per Ahl Haq Ulama. They are misguided and misguide those who follow them.
(3) It is not lawful as per the Ulama of Ahl Haq to trust Ghair Muqallid Ulama leaving four Imams as it is mentioned above. It is server deviation to consider that they know the holy Quran and Hadith better than four Imams.
Allah knows Best!
Darul Uloom Deoband