dont

White have a pined rook by bishop on a6, but the best move is not take this rook because imediately black stay with one peace advantage. In despite 2. ...Rd6 pinning the bishop d7 the white have Qxe5+ followed by Nxe5 and if black moves ...f6 to take back a piece white, at least, can take b4-black-pawn and the king threating take c3-black pawn. For all these reason the best move for black is advance his b4-pawn looking for c3-c2 to promove a queen. If white answers 1. ...b3 with 2.Nxe5 then black moves 2. ...c2 (Not 2. ...b2 because white have 3.Rf1 trying get some counter play since queen control g6 square and Knight too). 3.Kd2 b2 4.Rc1 b1=Q or 4. ...Bxd3 , well, the black wins!

http://dont

Amateur

I think Carlos has found Black's best move 1. ..., b3. Let's see whether 
White has any defensive resources to prevent Black's powerful connected passed pawns from queening.  
(A). 1. ..., b3 2. QXe5+, QXQ 3. NXQ, b2 4. Rb1, c2 (B). 1. ..., b3 2. Ba4, b2 3. Rd1, c2 4. BXc2, QXB+ 5. Ke3, b1:Q 6. RXQ, QXR+ 7. Kf2, QXR (C). 1. ..., b3 2. Ne1, b2 3. Rd1, c2 4. NXc2, QXN+ 5. Ke1, b1:Q 6. RXQ, QXR+ 7. Rd1, QXe4+  
There may be other, more accurate variations and with best play Black should win.

Amateur

Another variation runs as follows: 
1. ..., b3 2. NXe5, b2 3. Rf1, Qd6! anticipating RXf7+ by guarding g6, pinning Ne5 and threatening c2.

Amateur

Sorry, in yesterday's variation 1. ..., b3 2.NXe5, b2 3.Rf1, Qd6! White could reply with 4.Ba4 Better is the following continuation: 1. ..., b3 2.NXe5, c2 (suggested by Carlos) 3.Rf1, c1=N+ 4.RXN, QXR (If 4.Ke1, NXR+ 5.NXN, Qc3+ 6.Ke2, Qc2+ 7.Ke1, BXN threatening mate).