Drinking from Zamzam is mustahabb, not obligatory
Question

                I intend, if Allaah wills, to do ‘Umrah during the blessed month of Ramadaan. I am supposed to reach Makkah by land at noontime. It is well known that the pilgrim doing ‘umrah has to drink some Zamzam water after praying behind Maqaam Ibraaheem on ordinary days, but in Ramadaan I intend to fast and not break my fast. So how can I drink Zamzam water?.
Praise be to Allah.
    Firstly: 

    Drinking Zamzam water is not obligatory, rather it is 
    mustahabb, but it is not mustahabb only after praying the two rak’ahs behind 
    the Maqaam, rather drinking from Zamzam is mustahabb at all times. 

    Shaykh al-Islam said in Majmoo’ al-Fataawa (16/144): 
It is mustahabb to drink 
    Zamzam water and to drink one’s fill of it, and to make whatever Islamically 
    prescribed du’aa’s one wants when drinking it. 

    Al-Muwaffaq said in al-Mughni: 
It is mustahabb to come 
    to Zamzam and drink from its water for the one who wants to, and to drink 
    one's fill of it. Jaabir said, describing the Hajj of the Prophet  
    (peace and blessings of Allaah be upon him): “Then he came to Banu ‘Abd 
    al-Muttalib, who were providing water, and they gave him a bucket, and he 
    drank from it.” 

    Al-Nawawi said in al-Majmoo’: 
Al-Shaafa’i, his 
    companions and others said: it is mustahabb to drink Zamzam water, and to 
    drink a great deal of it, and to drink one's fill. It is mustahabb to drink 
    it for whatever benefits one wants in this world and the Hereafter. If a 
    person wants to drink it for forgiveness or healing from sickness etc, he 
    should face the qiblah and mention the name of Allaah, then say, “O Allaah, 
    I heard that Your Messenger  (peace and blessings of Allaah be upon him) 
    said: ‘The water of Zamzam is for whatever it is drunk for.’ O Allaah, I am 
    drinking it so that You will forgive me so forgive me, O Allaah,” or: “I am 
    drinking it to seek healing from sickness, so heal me, O Allaah.” And so on. 
    It is mustahabb to drink in three draughts as in the case of any other 
    drink. And when he is done he should praise Allaah. 

    Shaykh Ibn Baaz said in Majmoo’ al-Fataawa (16/138): 

    It is mustahabb for the pilgrim doing Hajj or ‘umrah to drink 
    from the water of Zamzam if he is able to do so. 

    Based on this, if you do ‘umrah when you are fasting, there 
    is no sin on you if you do not drink from Zamzam, and you can drink from it 
    after you break your fast. 

    Secondly: 

    If you are traveling to Makkah for ‘umrah, it is permissible 
    for a traveler either to break his fast or to fast, according to scholarly 
    consensus, but they differed as to which is better. We have already 
    mentioned in the answer to question no. 
    20165 that what is better is what is 
    easier. For those for whom fasting when traveling is not too difficult, then 
    fasting is better, and for those for whom fasting is too difficult whilst 
    traveling, not fasting is better, especially for one who is doing ‘umrah, 
    because he needs physical strength in order to do ‘umrah properly, with 
    du’aa’ and proper focus and humility. 

    Some people who do ‘umrah make it difficult for themselves by 
    doing ‘umrah whilst fasting, even though fasting is very difficult for them, 
    which affects the way they do ‘umrah. It was proven that the Prophet  
    (peace and blessings of Allaah be upon him) used to break his fast on the 
    Day of ‘Arafah. 

    Al-Shawkaani said: 

    Fasting the day of ‘Arafah is mustahabb for everyone, but it 
    is makrooh for those who are in ‘Arafah for Hajj. The reason for that is 
    that it may lead to the pilgrim becoming too weak to offer du’aa’ and 
    remember Allaah (dhikr) on the Day of ‘Arafaah in that place and to do the 
    actions of Hajj. 

    It was proven in al-Saheehayn that the Prophet  
    (peace and blessings of Allaah be upon him) forbade singling out Friday for 
    fasting. 

    Al-Nawawi said: 
It is makrooh to single 
    out Friday for fasting unless that coincides with one’s habit [e.g. fasting 
    alternate days], but if a person fasts the day after or the day before as 
    well, or it coincides with his habits, such as if he vowed to fast the day 
    when he was healed forever, and that happens to be a Friday, then it is not 
    makrooh. 

    The scholars said: The reason why it is forbidden is that 
    Friday is a day of du’aa’, dhikr and worship, such as doing ghusl, going to 
    the prayer early and waiting for the prayer, listening to the khutbah and 
    doing a lot of dhikr afterwards. Allaah says (interpretation of the 
    meaning): 
“Then when the (Jumu‘ah) 
    Salaah (prayer) is ended, you may disperse through the land, and seek the 
    Bounty of Allaah (by working), and remember Allaah much”

    [al-Jumu’ah 62:10]

    And there are other acts of worship to be done on this day, 
    so it is mustahabb not to fast on Friday, because that helps one to do these 
    duties in an energetic manner and to enjoy them without getting tired or 
    bored. This is similar to the situation of the pilgrim on the Day of ‘Arafah 
    in ‘Arafah – the Sunnah is for him not to fast as stated above, for the same 
    reason. If some one were to say: if a person fasts another day as Friday 
    that will still make him tired and affect his worship. The answer is that by 
    fasting an extra day he will gain reward that will make up for any 
    shortcomings in his worship on Friday. This is the reason why it is 
    prohibited to single out Friday for fasting. 

    Shaykh Ibn ‘Uthaymeen was asked in Fataawa Arkaan al-Islam 
    (p. 464) about a traveler who reaches Makkah fasting: should he break his 
    fast in order to have more strength to do ‘umrah? 

    We say: when the Prophet  (peace and blessings of Allaah 
    be upon him) entered Makkah on the twentieth of Ramadaan in the year of the 
    Conquest, he broke his fast. 

    It is proven in Saheeh al-Bukhaari that the Prophet 
     (peace and blessings of Allaah be upon him) did not fast for the rest 
    of the month, because he was traveling. The journey of the pilgrim doing 
    ‘umrah does not end when he reaches Makkah, and he does not have to refrain 
    from eating etc if he comes not fasting. Some people may continue to fast 
    even when traveling, because fasting whilst traveling nowadays is not a 
    hardship for the ummah, so they continue to fast whilst traveling then come 
    to Makkah feeling very tired, and they wonder whether they should continue 
    their fast or not, or should they delay ‘umrah until after they have broken 
    the fast, or break the fast in order to do ‘umrah straight after reaching 
    Makkah?

    We say to them in this case: it is better for you to break 
    your fast in order to do ‘umrah as soon as you reach Makkah, when you are 
    still feeling energetic, because the Sunnah is for the one who comes to 
    Makkah for pilgrimage to hasten straight away to do these rituals. When the 
    Prophet  (peace and blessings of Allaah be upon him) entered Makkah for 
    the purpose of pilgrimage he would hasten to the mosque, and he used to make 
    his camel stop at the mosque and go in to do his rituals that he had come to 
    do. Not fasting so that you will be able to do ‘umrah in an energetic manner 
    during the day is better than continuing to fast and then doing ‘umrah after 
    you break your fast at night. It was proven that the Prophet  (peace and 
    blessings of Allaah be upon him) was fasting when he was traveling to 
    conquer Makkah, then the people came to him and said: “O Messenger of 
    Allaah, fasting is proving too hard for the people, and they are waiting to 
    see what you will do.” And that was after ‘Asr. So the Prophet  (peace 
    and blessings of Allaah be upon him) asked for a drink of water and drank it 
    whilst the people were looking on. So he broke his fast whilst traveling, 
    and he even broke his fast towards the end of the day, all in order to show 
    his ummah that that is permissible. Making oneself fast whilst traveling 
    even though it is too difficult is undoubtedly contrary to the Sunnah, and 
    the following words of the Prophet  (peace and blessings of Allaah be 
    upon him) apply in this case: “It is not righteousness to fast whilst 
    traveling.” 

    If your fasting whilst traveling will affect your performance of ‘umrah, then it is better for you to break your fast and make that day up later on.