The winners, who needed an outright victory against the visitors in order to make it to the finals of the c'ship, rallied in a splendid manner through Pathan and Trivedi as they bundled out their opponents for a paltry 165 in their second essay and then scored the 27 runs required with 12 mandatory overs to spare.
West Zone will now take on defending champions and Group-A' topper North Zone in the final to be played at Mumbai from Feb 19.
With five points in their kitty, Lions needed just a draw in this tie to make it to the finals in their maiden appearance in Duleep Trophy. However they failed against a probing line of Pathan (Sr) and Trivedi.
Pathan and Trivedi, capitalising on the wearing pitch on final day's play, ripped through the Lions line up. Apart from Ed Joyce (66, 136b, 9x4) and Adil Rashid (39, 106b, 4x4) none of the English batsmen showed stomach for fight. Joyce and Rashid dug in to save the side from the ignominy of an innings defeat with sensible batting.
After reducing England Lions to 109 for five at lunch, West Zone demolished their opponents at 165 all out twenty-five minutes before tea, with Trivedi striking twice in as many balls. The Gujarat paceman trapped Liam Plunkett (5) and Graham Onions (0) leg before in two consecutive deliveries in his 13th over.
Chasing a slender victory target of 27 runs in as many overs, West Zone hit up 28 in 14.2 overs losing the lone wicket of Mumbai batsman Ajinkay Rahane.
A jubilant West Zone skipper Parthiv Patel attributed the team's spectacular victory to the record 342-run second wicket stand between Wasim Jaffer and Ajinkya Rahane, that helped the side gain a sizeable lead, and splendid bowling by Pathan and Trivedi, who restricted England Lions to 165 in their second knock.
''It is a good fight back. Now we have a big opportunity to grab the title in the finals,'' Patel said.
England Lions 355&165 all out (Ed Joyce 66, Adil Rashid 39; Yusuf Pathan 5 for 35, Trivedi 4 for 28) lost to West Zone 494&28/1.
At Rajkot: North Zone 360&459/2 (Akash Chopra 205 n o, Mithun Manhas 205 n o) beat East Zone 143&243 (Vardhan 83, Mazumdar 82) by 433 runs.