It seems like the Italians need at least some German 88s and a few Mark III tanks to hold in Libya for a while. Otherwise expanded Lend Lease from an early British victory might be enough to offset the small German gain in strength (assuming the extra Germans can be supplied in the Soviet Union). (If Greece is still Allied controlled in this TL, then non lethal stuff lend lease aid could be sent through the Black Sea through Turkey.)
Best case scenario for Germany:
a) Italians don't invade Greece
b) Italians are able then to send just a little extra supply and a few more mobile forces and air into Egypt.
c) Before the British OTL attack the Italians send a smallish mobile column toward Matruh.
d) This is of course cut to pieces by the British.
e) The Italians evacuate their static infantry from Egypt to the Libyan frontier.
f) The British, content Egypt is safe, withdraw 4th Indian division to East Africa (as like OTL) but Operation Compass never happens like OTL.
g) The British then leisurely prepare for a major North African offensive starting April (perhaps taking time to extend railway from Matruh) and finishing out East Africa in the meantime.
h) The Germans send a single Panzer division block force and the OTL contingent of 88s. (with a defensive minded general who can work well with the Italians).
i) Extra Italian forces are available without Greece (early M1340s etc.).
j) The small/German large Italian blocking force hold the Libyan frontier with its natural defenses indefinitely.
h) Instead of raiding the Germans put Bismark and Prinz Eugen in Alta, Norway as a fleet in being (this makes enlarged Lend Lease impracticle)
The 1 extra Panzer division, and other forces not needed in the Balkans are available for Barbarossa. Barbarossa happens June 15th, (spring mud, and other logistical and preparation issues delay offensive until then anyway). Crete doesn't happen here so lots of Ju52s are available, perhaps these help keep supplied the larger force.
Lets assume the extra forces are used in the north, where the better air strip facilities of the Baltic countries, allow for the extra forces to be supplied. Leningrad falls in August/ early September (Zhukov killed), the extra forces sent to support Typhoon, Stalin and what ever general he puts in charge now that Zhukov is dead is a more dysfunctional relationship, slightly better German performance, one more week of good weather results in panic, Moscow abandoned. Follow up operations in 1942 secure Stalingrad and Grozny. Soviet front then settles into a stalemate on the Don/Volga with neither side strong enough to advance.