I may be wrong here but my thinking is: ZTS has a market cap of 17.22 based on today's price. Pfe is essentially selling 80%. At today's prices Pfizer will reap 13.78 billion dollars in value (.80 x 17.22). Granted this is in the form of a stock buyback which essentially will drive the share price up accordingly. Pfe is unlocking the value of the shares sitting in paper and putting them to use (did the previous market cap already factor this in?). Pfe's market cap yesterday was 204.12. After the ZTS transaction it is effectively is 217.90. this is an increase of 6.54% in unlocked value. yesterdays price was 28.79; an increase of 6.54% yields a new share price of 30.67. we still have some upside on this news. am i correct?
Well, in the efficient market scenario, PFE should not change value due to ZTS offer. The company is offering its shareholders a deal. It is like you are offering a deal to yourself, your net worth doesn't change.