Tony:
It really depends a lot on your development environment. From your list of computers you have available, I didn't see anything "modern". WINDOWS-XP support was discontinued at least a decade ago and WINDOWS-7 support was discontinued at least a few years ago.

Personally, I USED to run WINDOWS-98 and the WINDOWS 2000 for a few years in the late 90's but all the while, I had always looked into the new but evolving OS called Linux, which wasn't ready for me at the time. Eventually, when it hit kernel version 2.4.2x in early 2000's, I decided to take the plunge and installed SLACKWARE on my main INTEL-based PC. I ran WINDOWS as a secondary computer "just in case". These days, I run Linux MINT and have not run WINDOWS as a main OS in almost 2 decades. I have all my computers set up to run a small-footprint Linux but can multi-boot into WINDOWS, DOS or a Linux-based rescue tool. I also run a Linux-based file server that operates 24/7 and supports SMART drive monitoring and software RAID with drive mirroring for redundancy. I do however, run WINDOWS-XP and WINDOWS-7 as virtual machines (VM) under Linux on my main laptop computer (TOSHIBA Satellite series circa 2011) using ORACLE's Virtual-Box, which works quite well. I've set other systems up as virtual machines such as DOS, XENIX and OS/2 WARP and they work well ... and bring back some OLD memories. :) The only reason WHY I still run WINDOWS as a VM is because when developing for the ATMEL/MICROCHIP AVR8 series of MCU's, I still prefer AVR STUDIO 4.19 over any newer version of AVR STUDIO (bloated and requires WIN-10!). For my hobby-based needs, I also use an ancient version of OrCAD/ALLEGRO for schematic capture and PCB creation, which is WINDOWS based as well but there are several free capture and layout packages available for both Linux and WINDOWS environments. There are other development tools whose only supported development environment is targeted for WINDOWS. This includes the GARMIN map updating software for my GPS. (Sigh..) I can't individually verify but I think some of the OEM's like XILINX have started to port their tolls for Linux or WINDOWS as many design engineers are using Linux for their development environment.

Linux, as a development platform, brings in many open-source projects and generating executables from source code is generally built in with the (free) GCC and G++ compilers, so unlike WINDOWS, you don't have to purchase a C compiler package. There are also many (free) tools and techniques for handling HEX, SREC and binary files, including concatenating several HEX files in a binary ROM image. Essential tools for working with the 8-bitters of the past. I prefer the SREC tools for such occasions. With Linux, there are also tools and techniques for interacting with your VM's virtual serial-I/O and virtual network cards using either the various Linux terminal emulators (I like PICOCOM) or even using SSH from a different (networked) computer altogether. In the past, 1990's, I spent many hours writing DOS and OS/2 batch and command files to support various situations on various computers in my employer's small engineering house. 4DOS/4OS2 and REXX really helped in that situation. Now, under Linux, developing custom scripts is so much easier and using pipes for inter-program communications at the scripting level makes things so much more versatile and easier. I can create an entire software build script? under Linux that will assemble, link and upload my code to my target platform.?

In summary, your choice of development environment will dictate what tools you will have available to use.

On the Z80 development, as Josh stated, different assemblers have different features and abilities. And of course, that also depends on their supported host platform too! These days, you can find a lot of DOS-based tools (like TASM) available for free. Even some of Dave Dunfield's DOS-based tools are available and still function well under Linux's DOSBOX and QEMU. For the WINDOWS command line tools, you can use WINE, a WINDOWS emulator for Linux. There are a few assemblers available that can be compiled for Linux, WINDOWS or MAC-OS executables. There are also Z80/CP/M simulators that can target different host computers (including AVR and PIC) as well as C64, ZX80, ALTAIR, AIM65, KIM-1, APPLE I, II, PDP-11, etc. software simulators available, so getting back into the 8-bitters of the past is much easier, much less costly and much more enjoyable to enter into. Many of these simulators have built-in debugging features that one would have had to pay $$$$ for the hardware version "back in the day".

And yes, I compliment Josh on his exceptional commenting abilities in the Z80MBC monitor's source code. And yes, Josh, I've spent many hours studying your code. :)

Here are the assemblers I currently have installed under Linux. Generally speaking, I try to use an assembler that assemblers someone's source code without too many errors. Its likely that you'll have to massage code to match your choice of assembler's syntax and such but using a search-and-replace function in your editor (I use MEDIT) speeds that sometimes extremely tedious task up for you.

Josh uses Bruce Tomlin's ASMX for the Z80MBC assembly.

Also, there are a few C compilers available for the Z80. SDCC seems to be the primary choice.

BTW: I still have my APPLE //e, APPLE //gs and a 512K MAC-SE in storage. I used to develop software on the APPLE //e for a laser-show project I hobby-designed back in the mid-80's and used the SC-MACRO assembler to develop the machine-language routines.?

I hope some of the info I conveyed will be of use to you.

Peace and blessings,
Scott