@GW4DVB Hi and welcome. I've just done sone searching and think I have found your answer why you are experiencing problems:
"The MacBook Pro 5,1, released in 2010, features an integrated NVIDIA GeForce 9400M graphics processor with 256 MB of shared memory (up to 512 MB available in Windows via Boot Camp). It does not have a dedicated graphics card."
This means your graphics memory is shared out of your RAM like early Windows notebooks so instead of having 4 Gb RAM available you will only have access to 3.75 or 3.5 Gb RAM.
I've stated on another thread that Team Zorin should put the 'Try Core first before purchasing Pro' further up the page. Personally I would give Q4OS a try. I installed it on a rig I built in 2006 with a single Athlon Processor, 2 Gb RAM, and 512 Mb 8x AGP graphics card from EVGA, It just about runs. It uses a much lower kernel, 6.1.x and it is free to download. I would use the Plasma version which has a Look Switcher that gives a MacOS theme at no cost with 2 variants, Dark and Light.
I would contact the team and ask for a refund.