On the ITBusinessEdge site, there's a quick column from Lora Bentley looking at things from the other side of the Zend/Microsoft story - Microsoft's.

She mentions the "about face" that Microsoft has seemingly made when it comes to Open Source projects, specifically the Zend deal:

As a DigitalJournal writer pointed out yesterday, the deal makes great business sense for Microsoft, given that PHP runs more than 2 million Web sites and the software company's servers and tools business contributed one-fourth of its total revenue in the latest quarter.

You can get complete information regarding the collaboration from the Zend website.