The major product formed in the following reaction is

Concept:

• Grubbs catalysts are Ruthenium containing Metal-carbene complexes, named after Robert H. Grubbs
• These complexes are used in olefin metathesis reactions, also known as Grubbs reaction.
• Metathesis reaction between 2 olefins involves formation of 4 membered ring, followed by rearrangement of the bond to get new olefinic bond.

Explanation:

• In the first step, the Grubbs catalyst exchange the groups  and form carbene with ethylene molecule           
• In the next step, the Ru-olefin carbene complex undergoes [2+2] cycloaddition reaction with the double bond present in given substrate      
• Further, 4 membered ring containing Ru will undergo rearrangement leading to ring opening. The Ru=C bond  again shows cycloaddition with another ethylene molecule to give 4 membered ring followed by rearrangement and ring opening to get double bonds with different substituents. 
•            
• Finally, there will be Sigmatropic rearrangement.        

Conclusion:

Therefore, the final product of given Grubbs reaction is :