ZYX Compilance

ZYX compliance measured at 100Hz just like nearly all Japanese cartridges. 

You have to multiply on 1.7 to convert this figure to 10Hz 

You need Hi Fi Test LP to measure actual resonance freq. of your arm/cart. The range is 8 - 15 Hz, why do you think you need 11 Hz?? Change headshell if you want to tune the resonance freq. 

I've been using my ex Zyx cartridges on EPA-100 and Reed 3P "12. With EPA-100 you can use different headshells, with Reed you  an choose the mass and length of the arm when you're buying the arm ("9, "10.5, "12 inch available from the manufacturer). Special mounting screw for a cart can change the mass a bit. 

@dolphytrane forget about static compliance, only dynamic compliance is what we need to choose the arm. Vinyl engine is a source with a lot of misinformation when it comes to data. ZYX dynamic compliance is 15cu (horizontal) and 12cu (vertical), both measured at 100Hz.

To convert it to 10Hz we have to multiply on 1.7 (not on 2.2).
So everything you have written is wrong. Where did you get your data, do you have ZYX cartridge ? I have original manual on hands from my ex ZYX Premium 4D SB. Static compliance does not even mentioned in the original printed manual for ZYX (because nobody need it).

at 10Hz ZYX compliance is about: 
25.5 cu (lateral)
20.4 cu (vertical)

This is medium dynamic compliance and it’s quite normal for a modern LOMC. This is the reason why ZYX is fine for most of the modern tonearms.

I do have a Zyx cartridge & in my manual it simply says ’Compliance’ it does not state whether it is Dynamic or Static or what it is measured at either 10hz or 100hz, hence the reason for starting this topic.
If the compliance is how you have calculated at 25.5cu & using your ETA arm, according to the manual its effective mass is 22g with a 6.5g cartridge, I don’t know the weight of your 4D but my cartridge weight with SB is 7.9 so this would increase the mass with the ETA to 23.4g using the calculation in the article link by rdk777 we get an RF of 6.5 it is also stated in this article that the desired range is 9-11 so your combination is well outside the range.

My EPA-100 (not ETA) has been in use with ZYX Airy III without Silver Base, don’t forget that EPA tonearm has a very special counterweight mechanism to deal with cartridges with different compliance, you can read in Technics EPA-100 manual, this is unique option, no other tonearm will give you something like this. 

If we aim for an RF of 10 right in the middle of the desired range using your calculation of 25.5 compliance & my cartridge weight of 7.9g I would need an arm with effective mass of 21g. I would really appreciate your recommendations of an arm in this range.

Reed 3P "12 Cocobolo was my second arm when i upgraded from ZYX Airy III to ZYX Premium 4D Silver Base (7.9g) , the effective mass of my Reed tonearm was 18-19g (without cartridge). Reed is an excellent toneam for any cartridges, you can buy Reed in 9.5, 10 or 12 inch length and each wood has different mass, so you can buy what you need. Absolutely amazing tonearm with so many unique features. 

P.S. You don’t have to worry that much to keep your arm/cart resonance at 10Hz, this is theory, practically you will not hear the difference anyway, just try to stay in the range of 8Hz - 15Hz.

I can't because i no longer use ZYX since i discovered better  cartridges for my needs. 

But i told you that you can buy Reed with lower effective mass if you will look at shorter cocobolo armtube (10.5 or 9 inch) or just different wood for armtube, reed have many options.