Vidarbha's left-handed opener Faiz Fazal (127, 280 balls) and Sudeep Chatterjee (54) of Bengal held the innings together for the first part while Karun Nair (92, 132 balls), Stuart Binny (54 off 51 balls), Sheldon Jackson (59 no) pounced on the opportunity to pulverise a below-par bowling attack taking the team to victory in 129.4 overs.
Starting the day at 100 for 1 and needing 380 more runs on the final day to achieve the third-highest successful run-chase in Indian first class cricket history, Rest achieved the target with 20 balls to spare.
Though Mumbai fought back with left-arm spinner Iqbal Abdullah (5/154) striking thrice in quick time to pack off this trio of batsmen, and captain Naman Ojha (29) was run out brilliantly, Rest had enough quality batsmen - especially the hard-hitting Binny - to overhaul the stiff target from their tea score of 321 for 3.
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Binny, who struck two towering sixes - including one into the press box on the second storey of the club house - and also hit three fours, fell when Rest needed 35 runs, caught cutting Abdullah at point.
Jackson, who remained unbeaten after facing 76 balls
and striking four fours and a six, and Jayant Yadav (19 not out) helped the Rest cross the finish line with ease in the end, the former also fittingly hitting the winning shot - a four. Their unconquered seventh wicket partnership was worth 37 runs.
Abdullah was the most successful bowler with a five-for but he lacked adequate spin support. Mumbai were also let down by their trio of medium pacers - Dhawal Kulkarni, Shardul Thakur and Balwinder Singh Sandhu -who, looked pedestrian and spoilt Mumbai's huge 297-run first innings advantage.
The successful run-chase was also the third-highest in the Indian domestic first class history.
The highest remains West Zone's incredible chase of 536 riding on Yusuf Pathan's 210 in the 2010 Duleep Trophy final at Hyderabad followed by South Zone's successful chase of 501 on the back of Venugopal Rao's 228 and centuries from S Sriram and S Badrinath in a Duleep league game at Gurgaon in 2004.
Brief scores: Mumbai 603 and 182 lost to Rest of India 306 and 482 for 6 (Faiz Fazal 127, K S Bharat 42, S Chatterjee 54, K Nair 92, S Jackson not out 59, S Binny 54, J Yadav not out 19; I Abdullah 5 for 154) by four wickets.