Well, Zakheim gets an automatic fail on credibility from me:

1: “If anything, we’re likely going to take a much tougher line on Iran, which will please all the rest of the Arabs in the region,”  
• Iranians are Persians, not Arabs. One of the easiest things to get straight in that region. Or he just prefers to lump everyone in the Middle East into one or two categories/interests when he's advising.

2: Zakheim served as a foreign policy advisor to George W. Bush as part of a group led by Condoleezza Rice that called itself The Vulcans.
• The Vulcans was a nick name for the worst of the lot in Washington, i.e. Richard Armitage, Rice, Richard Perle, Paul Wolfowitz. The people that made the lies that pushed the agenda to invading Iraq for BS reasons.

3. Zakheim apologizes for Trump's words and actions at every step, according to his statements quoted in this article. Another suck up who formerly denounced Trump and is now covering his options ($ and influence) instead of his principles.