Quatrain 20

گیرم تو به ادراک معمّا نرسد
در نکته‌ٔ زیرکان دانا نرسد
اینجا ز می لعل بهشتی می‌ساز
کانجا که بهشت است رسی یا نرسی

Dashti, quatrain 49, p. 253

giram to be edraak-e mo‘ammaa narasi
dar nokte-ye zirakaan-e daanaa narasi
injaa ze mey-e la‘l beheshti  misaaz
kaanjaa ke behesht ast rasi yaa narasi

O heart! that riddle thou wilt never read,
That point on which the wise are not agreed;
Quaff wine, and make thy heaven here below,
Who knows if heaven above will be thy meed?

Whinfield, quatrain 427

These problems you will never understand,
So leave them to the subtle men of science.
Make here your paradise with ruby wine;
That other you may see one day - or not.

Elwell-Sutton, In Search of Omar Khayyam, quatrain 49, p. 195

Translation & Discussion of the quatrain:  The speaker appears to acknowledge that the only control is over the "now"; "you" can't solve the riddle of existence and you can't be sure where you will end up once life ends.  Another well-known bit of advice against the not-trying-to solve this riddle and what is more important to do is found in Hafez, ghazal 3 (in both the Qazvini, line 8, and Khanlari, line 5, editions):

حدیث از مطرب و می گو و راز دهر کمتر جو
که کس نگشود و نگشاید به حکمت این معمّا را

hadis az motreb o mey gu o raaz-e dahr kamtar ju
ke kas nagshud o nagshaayad be hekmat in mo‘ammaa raa

Let's talk of wine and music, not
Of fate, and how the heavens revolve-
Theirs is a riddle no man's wisdom
Has solved yet, or ever will solve.

Dick Davis, Faces of Love, p. 128-129

1 & 2. I concede/grant that you will not arrive at the understanding of the riddle/you will not grasp/solve the riddle & you will not reach it/get there through the subtleties of the learned problem-penetrators -- giram, "granted, allowing, given", 1st sing. of the present/future of gereftan- "I take it that". zirakaan: I think this means "those who get to the core of things and penetrate problems by their perceptiveness.  The conjunction of zirakaan-e daanaa, words of similar meaning, underscores the irony, the speaker conveys and the listener will understand, cf. weblog Quatrain 8, این بحر وجود and this quatrain, Dashti 3, p. 244:

آنانکه محیط فضل و آداب شدند
در جمع کمال شمع  اصحاب شدند
ره زین شب تاریک نبردند برون
گفتند فسانه‌ای و در خواب شدند

aanaanke mohit-e fazl o aadaab shodand
dar jam`-e kamaal sham`-e ashaab shodand
rah zin shab-e taarik nabordand berun
goftand fasaanei o dar khaab shodand

The saint and seer profound in wit and lore,
Who torch of knowledge 'mongst the sages bore,
Out of the darksome night could find no way;
Some tales they told, then went to sleep e'ermore.

Saidi, quatrain 57

The Revelations of Devout and Learn'd
Who rose before us, and as Prophets burn'd,
Are all but stories, which, awoke from Sleep
They told their comrades, and to Sleep return'd

FitzGerald, Stanza LXV, 4th ed.


3 & 4. Here, build a paradise of ruby wine/since there, which is paradise, you may or may not reach.