"Much of both companies development work," should read, "Much of both company's development work."
Actually I think since companies is plural, and it is posessive it should be "companies' ".
The following is from:
http://www.commerce.usask.ca/faculty/phillips/COURSE2/201MAIN/Media/writingguide.htm
The following examples are intended to clarify the
differences. Company is singular, company's is singular-possessive, companies is plural, and companies' is plural-possessive, and would be used as follows. "The
company's auditor provides advice to many other companies. Several companies' CEOs sit on the board of your company."
OOOPS! Sorry. Someone already mentioned this.