Corrects the description of deal in paragraph 5 from All cash to All Stock.

By Svea Herbst-Bayliss

BOSTON (Reuters) – Proxy advisory firms Institutional Shareholder Services and Glass, Lewis & Co on Friday told investors in Zendesk (NYSE:) to vote against a planned takeover of Momentive Global, the parent of web-based survey portal SurveyMonkey, arguing the deal is too risky.

After a few prominent shareholders opposed the deal, both ISS (and Glass Lewis) have voted against it. There are less chances that shareholders of the software company will vote for it later in the month.

“We believe Zendesk’s proposed acquisition of Momentive could readily be characterized as a case of, ‘ready, fire, aim’,” Glass Lewis analysts wrote in a note, adding, “we recommend shareholders vote AGAINST this proposal.”

ISS said that support for the proposal was not warranted and noted the many uncertainties surrounding revenue synergies, financial projections, and that this “had potential to become the rarest of particular situations,” a merger that shareholders both of the seller and buyer dislike.

Zendesk purchased Momentive for $4 billion in an all stock deal. Investors, including Jana Partners, an activist hedge-fund, swiftly criticized the proposal and questioned its financial viability.

Glass Lewis agreed and wrote: “We do not believe Zendesk investors — perhaps seeking some stability in the wake of the Company’s seesawing quarterly performance — have been afforded persuasive reason to conclude the Company is well positioned to efficiently realize the lofty objectives underpinning the Momentive transaction.”

Zendesk stated that on Thursday it received takeover interests but declined a bid of $127-132 per share from private equity groups and decided to move forward with the purchase of Momentive.

Corrects the description of deal in paragraph 5 from All cash to All Stock.