So I went and double checked it, its actually fully enhanced values. Forgive the poorly formatted DATA. I also tested resistances because why not at same time.
Zombies
HP Default
Base: 575
Upgrade: 626
Result: +51
HP Enhanced
95%: 677
127.7%: 692
159.9%: 709
Grave
HP Default
Base: 769
Upgrade: 822
Result: +53
HP Enhanced
95%: 874
127.7%: 891
159.9%: 908
Lich
HP Default
Base: 964
Upgrade: 1012
Result: +48
HP Enhanced
95%: 1058
127.7%: 1073
159.9%: 1088
So like if you take the +51 hp a zombie gets, multiply it by 2.599 (159.9% enhancement value), you get 132, add that to their default hp of 575 and it gets you to 707 (so my laziness in not using all the decimal points is probably why hp is off by 2)
So as you can see I was slightly off, Lich actually gains the least hp both % of total hp and raw amount and my non math estimates of "150" were only because I went all in on over enhancing. Still, the maximum values were simply 6 basic 50+5 IOs and Alpha slot but that results in basically 23% more hp total. A bit overkill in slotting but I was curious what a simple maximum was, and then also did a more 'normal' maximum of 3 SOs and then somewhere in between to represent set bonuses and such. Still it could be really nice especially if you can hit resist or dodge caps....
And while at it I tested the resist numbers with same basic enhancement plan
Zombies
Base: 20.25%
56%: 31.77%
75%: 35.46%
99%: 40.25%
Grave
Base: 27%
56%: 42.24%
75%: 47.28%
99%: 53.67%
Lich
Base: 33.75%
56%: 52.65%
75%: 59.1%
99%: 67.09%