Q.) Can you combine Zuhr with Asr and Maghrib with Isha salat while traveling? What do the different madhabs say about this? JazakAllahkhair.

A.) According to the Hanafi school, it is not permitted to combine the prayers and take a prayer out of its prayer time by either delaying it or performing it before its time. The only exception they have in this, based on the narration of Abdullah ibn Mas'ud, is in Arafat (where Zuhr and 'Asr are combined) and in Muzdalifa (where Maghrib and 'Isha are combined). The remaining three schools permit combining in other circumstances too as when a person is traveling, or it is raining heavily, etc.
There are many ahadith related on this issue and have been discussed by the four schools. The Hanafis have judged all the narrations on this issue to be based on the method of "apparent combining" [Jam' al-Suri] not "real combining" [jam' al-Haqiqi]. This position is based on the fact that we are told to make every prayer on time, and there are ahadith of Ibn Mas'ud which clarify that the Prophet (Sallallahu Alaihi Wasallam) never combined the prayers together [by taking a prayer out of its time] except in 'Arafat and Muzdalifa during the pilgrimage.
The following, which is an excerpt from the Fiqh al-Imam: Key Proofs in Hanafi Fiqh may be useful in understanding the ahadith on this issue:
3. 'Abdullah ibn Mas'ud, (RA), relates: I never observed the Messenger of Allah (Sallallahu Alaihi Wasallam) perform any prayer out of its time except at Muzdalifa. He combined Maghrib and 'Isha at Muzdalifa (Sahih al-Bukhari 1:227, Sahih Muslim 1:417, Sharh Ma'ani 'l-athar 1:164).
4. Another narration of Ibn Mas'ud, (RA), states: The Messenger of Allah (Sallallahu Alaihi Wasallam) combined two prayers whilst on a journey. He would combine Maghrib and 'Isha by delaying Maghrib until just before its expiry time, and performing 'Isha immediately as its time entered (Musannaf Ibn Abi Shayba 2:458).
5. 'A'isha, (RA), narrates: The Messenger of Allah (Sallallahu Alaihi Wasallam) whilst on a journey, would delay Zuhr and perform 'Asr early and would delay Maghrib and perform 'Isha early [i.e. perform each prayer in its own time] (Sharh Ma'ani 'l-athar 1:164, Musannaf Ibn Abi Shayba 2:457).
6. Ibn 'Abbas, (RA), narrates: I performed eight rak'ats together [four of Zuhr and four of 'Asr] and seven rak'ats together [three of Maghrib and four of 'Isha] with the Messenger of Allah (Sallallahu Alaihi Wasallam). [One of the narrators says,] "I asked Abu 'l-Sha'tha', 'I assume he delayed Zuhr [to the end of its time] and performed 'Asr as soon as it entered, and delayed Maghrib [likewise] and performed 'Isha early.' He replied, 'I also think the same'" (Sahih Muslim 1:246, Musannaf Ibn Abi Shayba 2: 456).
This hadith of Sahih Muslim is very clear about the exact description of combining two prayers. The method described by the narrator is jam' al-suri.
7. Imam Abu Dawud has transmitted the following: The muezzin of 'Abdullah ibn 'Umar informed him it was time for prayer. Ibn 'Umar, (RA), instructed him to continue on the journey. When the red of sunset [shafq ahmar] had nearly disappeared, he got of from his mount and performed Maghrib, then he waited until the red had completely disappeared and performed Isha. He then said, "Whenever the Messenger of Allah (Sallallahu Alaihi Wasallam) was in a hurry for some reason, he would do just as I have done" (Sunan Abi Dawud 1:178).
As we can see, the method of combining mentioned in the above ahadith is none other than that of jam' al-suri. It is an agreed upon method which nobody has any argument with. How can there be an objection to two prayers being performed together in a way that does not cause them to be performed either before their stipulated time or after it? Undoubtedly, this is the safest method of combining two prayers, and would be the most suitable way to explain the ahadith on combining.
It is also common knowledge that the Fajr prayer should not to be performed before its time or intentionally delayed beyond it. Similarly, other prayers should not be performed out of their stipulated times either, especially not while considering it to be sunna. This indicates that the sunna method of combining two prayers is jam' al-suri, as has also been substantiated through the Qur'an and Hadith. This is the Hanafi opinion in this issue.
If it was permissible to practice jam' al-haqiqi in the event of travel or illness, etc., then why is it confined to some prayers only? Why is it not permissible to perform all the prayers of the day together in the morning before departing on a journey? The reason for this is quite simple. The practice of combining mentioned in the ahadith is not to be taken as jam al-haqiqi, but as jam al-suri wherein each prayer remains in its own time, but are performed one after another....
And Allah knows best.

Q.) Is it permissible to establish second Jam'at in a Musjid?

A.) If Salat has been performed in a masjid which has an imam, then it is makrooh tahrimi to make a second jama'at of the same Salat inside the masjid proper. It is permissible to perform it in jama'at outside the masjid.
As for a musalla or a masjid that does not have an Imam, then it is permissible to perform more than one jama'at in such a masjid.
This is the standpoint of Imam Abu Hanifah, Imam Malik and Imam Shafi, as well as the majority of the fuqaha from the salaf (rahimahullah). Imam Ahmed gives permission for it, thus your quoting the practice of the Saudis has no bearing on the issue, as the majority of them are either Hambalis (followers of Imam Ahmed) or Wahabis, who are also proponents of its permissibility.
The reason for this karahat (dislike) is not the narration we have mentioned; the reason is that the permissibility of second jama'ats leads to a decrease in the number of people coming for the first jama'at, while one of the objectives of jama'at is to gather the Muslims together at one time.
In addition to this great harm, by granting permission for second jama'ats the door is opened for discord and disunity to set in, as any group that has slight differences with the Imam on any issue will then begin performing their own jama'at in the masjid.
One of the main reasons mentioned by Allah for Masjid-ud-dirar being built was to cause disunity between the Muslims, thus our pious predecessors (the Sahaba, Tabieen and A'immah), on the basis of what they learnt from Nabi (Sallallahu Alaihi Wasallam) made sure they closed this door on those who want to break the unity of the Muslims. Thus we find that the practice of the Sahaba, Radi-Allahu anhum, was that if they came to the masjid after the Salat was over, they would perform Salat individually. (Ibn Abi Shaibah Vol.2 Pg.113)
This was the practice of the salaf, thus we find it narrated from many of them that the second jama'at is makrooh, thus their practice was to perform Salat individually. Amongst those from which this is narrated is:
1. Qasim ibn Muhammad , the grandson of Sayyidna Abu Bakr, Radi-Allahu anhuma, and the great faqih of Madinah. (Ibn Abi Shaibah Vol.2 Pg.113)
2.Hasan Basri (Ibid)
3.Abu Qilabah (Ibid)
4.Hafs ibn Sulaiman (Abdul Razaaq
Vol.2 Pg.293)
5. Sufyaan Thawri (Ibid)
6. Abdul Razzaaq San'aani (Ibid)
7. Ibrahim Nakha'i (Abdul Razaaq Vol.2 Pg.292, Ibn Abi Shaibah Vol.2 Pg.112)
Cont'd on page 22
Cont'd from page 7
The practice of the Sahaba and the fatwa of all these luminaries is sufficient to establish karahat.
Now the narration about Nabi (Sallallahu Alaihi Wasallam) also points to the same, thus we have used it as well. Our opinion regarding our beloved Nabi (Sallallahu Alaihi Wasallam) is that he would not have left the great reward of performing Salat with jama'at in Masjid-un Nabawi, unless of course it was makrooh. Now when all the above proofs concur with this interpretation of the hadith, it is specified that this is its meaning.
And Allah Ta'ala Knows Best