FAMILY NAMES I. GIERUS is noted with Polish etymological works, here is the surname location in the present-day Poland: http://www.moikrewni.pl/mapa/kompletny/gierus.htmlhttp://www.moikrewni.pl/mapa/kompletny/gierus.html - 257 Poles surnamed Gierus, and some from SE Poland where the family cradle may be located, but most now in West Poland as resettled there after the WWII. II. ZIK is not Polish, seems the right is ZAK (¯ak) - a scholar, or ZUK (¯uk) - a beetle. You can see the surname location with the same search tool as above with Gierus.
II. FAMILY PLACES For now we have only one source - the ship Argentina manifest http://www.ellisisland.org/search/passRecord.asp?pID=100834020521http://www.ellisisland.org/search/passRecord.asp?pID=100834020521 - we see that the place of origin "Rawica" was absolutely wrongly read and written. According to Polish etymological works it could be in Poland as Rowna, Rowne, but I do suppose the right is Rownia (fully spelled in Polish as Równie): After deep search with historical databases I've found two Rownia in Austria - SE Poland: 1. Rownia, the colony to village Binarowa, gmina (commune) Biecz, powiat (county) Gorlice, settled mainly by Poles with Roman Catholic creed. 2. Rownia, the village, gmina (commune) Ustrzyki Dolne, pow. Ustrzyki Dolne - in the 19th century it was settled mainly by Ruthenians - Lemkos with Greek Catholic creed and religion, but also by Roman Catholics and Jews. Interesting is that this Rownia after WWII was given to the Soviet Union, and after 1951 it was given again to Poland, as Soviet Union take a part of Poland riched with cool. Thus, we can say all Poles (Gierus?) had been resettled from this Rownia to the East of Poland gained from Germany after WWII. = I cannot help you more for today, as I cannot find any Gierus' records in these two places in the present-day Poland, and I don't know which Rownia is the right one. Please try to find more with US databases. The best would be the petition for naturalization, where every immigrant had to state the exact place of birth.
Hope this helps in the search of roots and heritage of your Gierus and Zak/Zuk from Poland. Tad Warsaw, Poland