PCP is much finer-grained than Zabbix in terms of the metrics it makes available (esp. from the Linux kernel); not sure on Zabbix costs but PCP is quite light on all resources (mem, cpu, net) and very robust.
I've worked on production systems where everything else was failing (hardware, kernel, applications) but PCP kept chugging along, recording and telling the sad story to anyone that would listen.
PCP can export many hundreds of Windows-specific counters (which it accesses via the PDH APIs). The Windows build does need some love though, as the OP mentioned - its out of date and needs a regular contributor to bring it up to date with the latest PCP sources.
Then Vector should Just Work (tm) for Windows servers too.
I've worked on production systems where everything else was failing (hardware, kernel, applications) but PCP kept chugging along, recording and telling the sad story to anyone that would listen.