Zanjeer Zani/Qama/Tatbir is part of a Culture and has nothing to do with Islam or Islamic Laws, but when culture starts to break the Islamic values and laws, such culture is then not accepted.
Fatwa of Ayatollah al-Uzma Sistani:
The philosophy of mourning during 'Ashura', is to respect the symbols of religion and remember the suffering of Imam Hussain, his companions, and his uprising to defend Islam and prevent the destruction of the religion by the Bani Umayyad dynasty. These rites must be done in such a way that in addition to serving that purpose, it draws the attention of others to these lofty goals. So those actions which are not understandable and cause misunderstandings and contempt for the religion must be avoided.
Fatwa of Ayatollah al-Uzma Khamenei:
Is hitting oneself with swords halal if it is done in secret? Or is your fatwa in this regard universal?
In addition to the fact that it is not held in the common view as manifestations of mourning and grief and it has no precedent at the lifetime of the Imams (a.s.) and even after that and we have not received any tradition quoted from the Infallibles (a.s.) about any support for this act, be it privately or publicly, this practice would, at the present time, give others a bad image of our school of thought. Therefore, there is no way that it can be considered permissible.
In commemorating the martyrdom of Imam Husayn (a.s.) on the tenth of Muharram, some people hit themselves with a machete, or walk bare-footed on fire. Such actions defame Shi'ism and put it in a bad light, if not undermine it. They cause bodily and spiritual harms on these doing it as well. What is your opinion in this matter?
Any practice that causes bodily harm, or leads to defaming the faith, is **haram**. Accordingly, the believers have to steer clear of it. There is no doubt that many of these practices besmirch the image of Ahlul Bayt's (a.s.) School of Thought which is the worst damage and loss.
Fatwa of Ayatollah al-Uzma Khoei (ra):
If blood matam and hitting oneself with chains, which are practiced in Muharram, cause ANY harm or serious harm or ridicule the religion and sect then it is impermissible."
Grand Ayatollah Abul Hasan Esfahani (1860--1946)
He openly supported the stance of Ayatullah Muhsin Al-Amin on this issue.
"The usage of swords, zanjeer, drums, horns and the likes today, which have become common in mourning ceremonies on Ashura, is definitely forbidden and against religious doctrine."
Dayrah al-Ma'arif Tashayyo', v.2, p.531; A'yan al-Shia, v.10, p.378; Professor Hassan Shabir, Tarikh Iraq Mu'asir, v.2, p.340
Shaheed Ayatollah Murtaza Mutahhari
Blood matam in its present form does not have a rational or religious basis. It is a clear instance of deviation. At least, in the present day it causes Shi'ism to be questioned. Activities that do not have any relation to the goals of Imam Husayn (a) are razors, blades and locks. Striking the head with a blade is the same. This is a mistake. Some people take blades and strike their heads making blood flow -- for what? This action is not mourning."
Howzah va Ruhaniyat, v.3
Grand Ayatollah Fazil Lankarani
The philosophy of mourning during 'Ashura, is to respect the symbols of Religion and remember the suffering of Imam Hussain (a), his companions, and his uprising to defend Islam and prevent the destruction of the religion by Bani Umayyad dynasty. These rites must be done in such a way that in addition to serving that purpose, it draws the attention of others to these lofty goals. Obviously, Qama Zani does not have such a role and the enemies of Ahlalbayt misuse it. So those actions which are not understandable for the enemies of Islam and causes misunderstanding and contempt for the religion must be avoided.
Grand Ayatollah Makarim Shirazi
The mourning congregations have to do their best to hold this ceremony as magnificent as possible, they should not permit anyone to do some acts which vilify the religion and give pretext to the enemies using the name of mourning congregation, acts like using music instruments, striking heads by sword, etc.although some people do these acts due to their passion toward imam Husain (a), but they should express this passion in a way that is acceptable and admitted by Imam Mahdi (a)."
Grand Ayatollah Jawad Tabrizi
Mourning the five people of the cloak is of the most important signs of religion and the secret to the survival of the Shia. But, it is necessary for our dear mourners to refrain from actions which defame the religion and are misused by the enemies of Islam."
Istafta'at, question 2003, 2012, 2014