I found that picture about the Apple IIe without the cover:
https://commons.m.wikimedia.org/wiki/File:Apple_IIe_Inside.JPG
 According to the wikipedia Apple II had the same CPU as the Commodore 64. So from the Z80 totally different instruction set. Was it necessary to develop tools for apple II at all?

When the cover was removed you probably placed the monitor behind the computer. Which is good, to hold distance from the eyes.

 Why did the company choose the Apple II for development? I saw that it was shipped with diskette drive, which is probably important to delvelope software fast.
 Who wrote the Apple software to connect to the Z80 via parallel port? Was that an inside tool, or did you get it from some other company?
 

The Z-80 SoftCard is a plug-in Apple II processor card developed by Microsoft to turn the computer into a CP/M system based upon the Zilog Z80

This gives Apple II users access to many more business applications, including compilers and interpreters for several high-level languages.

Source: https://en.m.wikipedia.org/wiki/Z-80_SoftCard

According to the schematic there was no RAM on the Z80 expansion card, it took the memory from the Apple II. So practically the computer was converted to a Z80 based computer, because of the available software.
Schematic:
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Z80%20Cards/Microsoft%20SoftCard/Schematics/

 So this Apple system was connected to the real EP via Parrallel port.

 Do you still remember how the EP received the data from the Apple? I mean the Z80 was stopped and the memory was overwritten, or the Z80 of the EP has done the byte receive and memory filling? Was this connection also a debbuger where you could set breakponts and load the memory of the EP back to the Apple to review it?