My take on recent trading is that ESIO & ZIGO are being priced according to their relative book value & cash per share with far less than the usual concern for long-term fundamentals.

At prices of $5.10 for ZIGO & $6.35 for ESIO, this is how they stack up:

ESIO's cash per share is 89% of its market capitalization while ZIGO's cash per share is 58%. ZIGO would have to trade around $3.30 to equal ESIO's valuation for cash per share.

ESIO is selling at 44% of its book value while ZIGO is priced at 52%, so ZIGO needs to drop to $4.30 to equal ESIO's valuation for book value.

VALUES USED IN CALCULATIONS:
ZIGO Cash Per Share: $2.95
ZIGO Book Value Per Share: $9.72

ESIO Cash Per Share: $5.64
ESIO Book Value Per Share: $14.30

If cash and book value are all an investor is considering then ZIGO should go down once the merger was broken and ESIO would go up because it is no longer being held down by Zigo's lower cash & book percentages.

Since I believe ESIO's fundamentals are much worse than ZIGO's, I don't think ZIGO will approach the prices needed to match ESIO's much lower valuation. We'll know more after next Thursday how disparate the long-term prospects are for the two companies.