HaKatan, on the contrary, conquering EY is a Tora mitzva (Ramban Sefer Hamitzvot). As for the Gimmel Shevuot, they are not paskened in any of the codes. They are not Halacha but Aggadata. Moreover, even if they once were in place they no longer are either because they were only for 1,000 years (Rav Chaim Vital – BTW, the end of the 1,000 years more or less coincides with the beginning of the Crusades. Perhaps the “terrible punishment” is for not coming back) or because the nations gave permission at the San Remo Conference (Rav Meir Simcha) or because Hashem has called (Rav Soloveichik).
However, you are correct that for us Zionism is right up there with Shema Yisrael. Both are commanded by the Tora and are basic to Judaism. As Rav Tzvi Yehuda said, we are not Religious Zionists – we are Zionist because we are religious and religious because we are Zionist. The two are inseparable.
As for lessening the imporatance of other mitzvot, does it lessen the importance of my Shema that I put on tefillin?