If you want to know if the Nokia E7-00 is officially supported by Slackware ARM I think that the answer is: NO ... I don't think there is an installer that will work out of the box to install on the Nokia E7-00.
If you want to know if it is possible to get Slackware ARM running on the Nokia E7-00 the answer could be MAYBE (you will need to get your hand dirty and have a look at how the Slackware Community has gotten Slackware ARM running on non officially supported devices here
If you want to know if the Slackware ARM userland can run on the Nokia E7-00 hardware the answer is: YES
However there is a very big issue: the hardware comes with Symbian, meaning that there may be no linux kernel that will support all the hardware features of the E7. Getting any sort of linux on this thing may be difficult. The wikipedia page does not say what SOC is used in the phone but knowing this may help you focus your research on similar efforts that may get you a bootable kernel for the hardware.
Also the bootloader may be an issue ... if the stock bootloader does not support booting a linux kernel image you might haveto look into the boot loader too.