The Ultras does not support ATAPI-drives on the internal IDE-port.
I think that is the reason why you cannot connect an ATAPI ZIP-drive, a CD-ROM or SSD to the internal IDE-port.
I'm sure the SSD will work via the ARS-2000UP with a E4-Ultra.
The ACARD SCSI-IDE bridge adapter is a work around. They are hard to find and they are quite expensive.
At the time I purchased my AEC-7720U new I paid half the price you pay now for a used one.
By a quick search on ebay I found:
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ACARD ARS-2000LFS 68-Pin Ultra160 SCSI-to-IDE/PATA HDD Adapter ... for US $249 plus shipping
or for US $25 a
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ARS 2000D (AQUA RELIEF SYSTEM PORTABLE THERAPY SYSTEM)
... OK... the last one is not the think you need...
In the end the SCSI-IDE bridge adapter is not a feasible solution because it's too expensive and too rare. AND ... you still need the SSD.